Nice point when you mentioned the toughness of a magnet through the BH curve. I've never thought of that like this before. This type of looking at things means a lot to me. Thank you very much for sharing your passion with us.
So glad you found a different perspective on that aspects of magnets. I always find hearing a differernt way of looking at something tends to add depth to ones understanding, whether or not one fully agrees with the other perspective. I am having great fun shareing this stuff - it has been a great excuse to do someexperiments I havngt done since I was a kid or university student!
I finally broke down 2.5 Watt speakers from 1968 since the cones were extremely dried out by weathering and the magnets around the speaker cone still are strong. Ferrite magnets remain polarized by weathering if temperatures never got hot enough to unalign those magnetized dipoles that were originally locked in place. For nearly 60 years Ferrite magnets remain strong.
What an interesting data point on the longevity of ferrite magnets! I wonder how well modern Neodymium magnets will have held up in 60 years from now!?
the higher the tensile strength,,, basicly the hardness of the steel the harder it is to magnetize ,,such as the difference between a 16 penny nail vs a knife blade made from carbonised steel ..however there are certain conditions you can magnetize high grade steel if you heat the metal up to a glowing red and then keep a current or magnetic feild around the piece being magnetised long enough till the metall cools down it will hold a magnetic field longer and be strongr also. this a basic way of how neomydium magnets are formed ,,If you will watch how magnets are made on an industrial scale you will notice that they will heat the object that is being magnetised , is they will heat t he metal red hot and then will zap it with a similar setup that this video has shown for a few seconds with low voltage and high amperage.. after the metal cools they will zap it once more with around 30 or 40 amps and around 30 volts .. in the final stage. i have been wanting to try this with common metal materials i have laying around such as transformer cores , which is made from highly magnetic material in A/C transformers. A/C current will create a stronger magnet such as used in junkyard cranes because A/C current when turned off th emetal is returned to nuetral if they used DC current in those magnets i the junkyards then they would not be able to release the junk iron they pick up. A/C current creates a very very strong magnetic field although. but is used only in certain applications. to demaganitize a piece of metal then u use a/c currrent .
A nice discussion on magnets. I work with engineering loudspeakers and most of what you said is spot on. I think some of the permanent magnets have a higher B value, but you were speaking in generalities. Did you hear me saying that's not a steel magnet! It's a ferrite. Greetings from near Ottawa! Mark
Thanks! Steel - ferrite - oops! I find I say a lot of things wrong when making videos and dont always catch them in editing. Must have done it again. Greetings from near Carleton Place! I see your even nearer to me than Ottawa!
Thank you so much! I'm gradually getting more views. The are about half a dozen of my videos that have done well with 100k or more views each. Sometimes it takes TH-cam weeks or months to fugure out who to show my thumbnails to and then suddenly a video takes off. Also becomes easier over time. I wish I could predect which videos would get popular but it seems to be almosgt random. I didnt expect the 75 Ohm TV cable (transmission line and reflections) to be popular - best response so far so you never know!
When I was in elementary school, the science teacher hung an iron rod om strings from the ceiling, oriented north south...after a few months, it was weakly magnetized ( could pick up a few pins).. Two jobs ago, we had a magnetizer/demagnetizer. It was just a coil driven by 120VAC. Just push the button briefly to magnetize, hold it down and slowly withdraw the screwdriver to demagnetize it. Your videos should be shown in schools!
Thanks! I had not heard of the experiment you described. It must be that with magnetically soft iron or steel the domains are so easily changeable that the thermal energy in a conformable room is enough to gradually change the magnetic orientation. I will have to try that sometime, maybe with a piece of rebar. The one I remember from grade school is stroking a nail with a magnet to produce a weak magnet. I guess each school and science teacher had a preferred experiment. Demagnetizers - 10 years ago I was involved in some factory automation design sorting some small items the size of finishing nails. Problem was they would get magnetized. The company's solution - which I duplicated - was to take out the rotor from an induction motor and power the stator with 12 to 24V AC and slide a plastic jar of the items being processed though it. Worked perfectly!
@@ElectromagneticVideos As I understood it, the iron rod was magnetized by the earth's magnetic field, which is why it had to face north south..well, magnetic north and south. I remember reading an article that steel ships can become weakly magnetized over time...and this can cause navigation problems....at least before gps was a thing. The " Philadelphia Experiment" conspiracy theory about making ships " invisible" got its start from an experiment to degauss ships, making them " invisible" to magnetic mines...
@@scottthomas3792 There was a faster version of the experiment you describe - same idea but hitting the rod with a hammer to encourage the domains to re-arrange to the direction of the field. I never thought about the steel in ships - but makes sense. When I was a kid we had an compass stuck on the dashboard of my dads car. It had little adjustable magnets you could adjust to zero out the field from the car's steel. We never got it even close to perfect! I didnt know that was the back story to the " Philadelphia Experiment" conspiracy theory. Shows you how adding secrecy to something like that makes peoples imaginations run wild!
Wish I had seen this much earlier. I adjust the strength of magnets for and industrial application. We don't use an iron core with the coil. The material to be magnetized is the core. There is no need to have an extended time to magnetize the material, so for the current required, a capacitor is charged and then discharged into the coil. Since the magnet is centered in the coil, it is a one step process. When loudspeakers are made, the magnetic material is not magnetized until the speaker basket and magnet assembly is assembled. It is then magnetized. Look for videos of the process online.
So you just use the working coil of the device to do the magnetization - with huge burst of current from a capcitor - what a greast way to simplify the process. I had no idea speaker were magnetized like that. I'm amazed that the fine wires in the coil can take the current - but as in your example - a brief burst is all it takes. I guess for the same reason, not enough energy in the current spike to move the coil enough to damage it.
@@ElectromagneticVideos They don't put the current into the voice coil. The magnet assemby is inserted into a larger external coil with high current capacity. The coil I use at work can fit a 4X6 piece, up to 8 inches long inside the coil. The coil is from a 30 KVA power transformer. The winding is 6AWG. I'll have to look at the capacitor value at work. I do remember it is rated for 63 working volts. I think it is 33000 MFD. The entire cycle is over in about 200mS.
Another way, maybe better, is to charge a suitable capacitor and dead short it against the magnet coil. With some care, from the B and H diagram one can obtain the (co)energy density of the magnet metal per gram or cc and calculate the total magnetization energy required by the magnet in Joules. Then using a generous safety factor let that be the capacitor energy before the short
It would probably be better - certainly could be done with a much smaller power supply. And your absolutely right - do a calculation as to how much energy is needed and setup the system accordingly. And to do things cleanly, maybe a SCR or MOSFET as the switch to handle the current surge without eroding switch contacts.
@@paulcohen1555 No! So things like iron have relative a permeability in the 1000 to 100000s, meaning the B is that many times stronger for a given H field that it would be in air or free space with a relative a permeability of one. As we drive a core in to saturation, its relative permeability drops but will always be more than air. So go for a nice iron core, a bit thicker than your object to be magnetized so that the B field get scrunched together and gets bit stronger in the object to be magnetized.
Very cool. When recharging a magnet, I use a compass to determine the magnet's polarity. It'd be cool to demonstrate this for the community so folks can work on magnets that are not color coded.
That a great idea - a compass is such an easily available ideal for determining magnet polarity. Glad you though the video was coll and thanks for posting the compass idea!
Your tapping on the magnet reminds me of a grade-school experiment to make a (very) weak magnet: hold an iron rod so that one end points north and the other south and then bang on one end with a hammer for a while. This uses Earth's magnetic field to (feebly) align the magnetic domains (or is it shifting the domain boundaries?). Don't know if your video plans include a discussion of how magnetic shunts are used to current limit transformers (I think there were clues in your magnetic chain video), but I'm sure you could do it justice.
It seems for things like iron and steel its shifting the domain boundaries, but its really outside my area of expertise so I could be corrected by someone with more specialized knowledge. I have read that for things like computer disks and tapes the magnetic coating particles are each one domain, so presumably their direction has to shift rather than boundary moving. Maybe that's a way to make a really hard magnetic material? Your tapping the iron rod experiment is exactly the same thing - the jolt presumably supplies a bit of energy to allow domain some walls to move which is what I was trying to do by tapping. Interestingly all I remember from school is stroking a nail with a bar magnet - maybe we didnt have any nice big steel bard to play with :) Current limiting magnetic shunts: I have been thinking about that but it will have to wait till summer: I have an old 120V 100A arc welder that should be much easier to take apart to show the shunt than the 240V 200A one. Its in a shed in the yard behind feet of snow right now. Yea - there were clues in the chain video - its always a struggle limit things to keep the videos to a viewable length!
Thank you so much! I really appreciate that. I actually did teach at university for a while after finishing grad studies but ended up in the hi-tech industry for most of my career. I did enjoy the teaching part but truthfully would have gotten tired of it after teaching the same courses again and again. I still occasionally do stuff with a local university - usually judging their 4th year thesis projects or sponsoring/advising a particular project. For what its worth, many of my videos (including this one) are modified from material or labs in 2nd, 3rd, or 4th year Electrical Engineering of Physics courses or labs that I have either taken or taught or both. But what I try and do here is minimize or eliminate the science and math background that is usually needed to keep things accessible to a general audience, but still present things in a way that is sill meaningful and properly represents the (often more complicated) underlying theory.
Glad you liked it! I found magnetics amazingly interesting in university - had a great physics prof for the first EM course and also took his grad course on magnetic which was his specialty. His interest in the subject was infectious!
Nice video, very well explained. Just one minor correction - at 14:08 where you show the B-H graph, I think you have the B & H reversed because the flattening of the curve is supposed to be for the flux density B which is the saturation point. So H should be on the horizontal and B vertical axis.
Thanks! I just looked - the problem is sloppy labeling of the graph on my part. I drew the vertical scale on the left side and horizontal scale on the bottom of the graph. The B on the left is meant to apply to the vertical scale and poor positioning on my part placed it near the horizontal axis. Same for the H. Sorry about the confusion!
I haven't had to deal with such weak ferrites, but AlNiCo compositions a low enough coercivity that they're easily demagnetized. Always have to keep them shunted and away from NdFeB magnets. I once had to do a bunch of testing with mortar fuze components that used AlNiCo cores, and I had to make a jig to remagnetize them. I guess that's the sort of inconvenience that happens when you try to reuse something that was meant to be used once before exploding.
So I'm really curious having never had anything to do with explosives. What do you use the magnets for - some sort of fuse or trigger? I would guess the shock of an explosion would also tend to demagnetize them ...
@@ElectromagneticVideos A lot of munitions fuzes have to do elaborate things where timing and sensing is required. Where some of those things used to be implemented mechanically with clockwork, it's all done electronically now. The problem then is getting electrical energy to power the microcontroller(s) in a way that can have a long shelf life (i.e. no active electrochemical cells). There are setback and spin-activated dry-charged cells, pyrotechnic generators, and other stuff, but a lot just use a once-through linear electric generator activated by setback. A tiny magnet gets snapped through a coil by its own inertia, which generates a single pulse which can be stored and used to power everything during flight. That poor generator only does its thing once before it (and the rest of the circuitry) gets destroyed by the main charge.
@@PSUQDPICHQIEIWC Thats amazing. - and clever! Almost infinite shelf life and probably just e enough power to get things done. "That poor generator only does its thing once before it ... gets destroyed" I guess that so true for so many of our sophisticated weapons these days. And for many other things, microelectronics has become so cheap they are essentially expendable - RFID tags immediately come to mind.
Have you actually made magnets that way - cooling the metal down while in a field? I have never actually done that - would be neat to hear how well it works in practice!
@@ElectromagneticVideos happens when you forge something facing due north or south till it cools and you hammer lightly up and down the bar to a plannishing heat. Super annoying when you dont want stuff magnetized.
@@williammorris1763 Oh - of course! How interesting. How strong is the field - can you pick up a bunch of finishing nails with the accidentally magnetized item? Most normal iron and steel makes poor magnets - have you tried banging the item with a hammer when cool? That might demagnetize it...
@@ElectromagneticVideos enough to be annoying. Not sure about hitting it, i just use a demagnetizer. They sell mag/demag tools on amazon. Wiha? Like $20~.
Great and educational video, but i have a question: does it matter for how long the external magnetic field is applied to a weak magnet? If i charge a 2000uF capacitor bank to 400v and put like 5000A through my coil, will i end up with an extremely strong magnet?
Thanks you! The process of magnetization should happen very quickly - certainly the type of speeds we change the magnetic field in transformers for example. So if you setup a capacitor bank as you described and make sure there is enough charge to keep the peak current going for say 1/100th or a second it should work. The really nice thing about your idea is you can get away with much smaller wires that would be needed for a longer period of high current. It would be a great experiment to try and see if if it works (be careful with 400V!) . One thing to point out though - you will always be limited by the saturation and remanence characteristics of the material you are magnetizing so there will be a current value above which you get no greater permanent magnetic field.
@@rekinek1111 Your most welcome! I really enjoy questions like that - its so interesting to think about something clever like that. If you try it, I would be fascinated to hear the results.
@@ElectromagneticVideos i love your channel! Subscribed! What is the most effective way to magnetize magnets in industry? Do they just put it briefly in a high field or do they do anything else special?
@@weirdsciencetv4999 Well thank you! Welcome aboard :) You know, I don't know what the latest technology is for that and its a really interesting question - particularly for Neodymium these days. I did a quick google on Neodymium and one manufacturer does say exactly that - put it briefly in a high field. But you also wonder if there is any secret sauce that one or the other manufacturer may have developed and are keeping it a trade secret - a particular charging current profile maybe that works best? Some other trick? It would be fascinating to see how its done in a real factory.
Can you detail how the coil is working? i need a magnetizer, and I have some coils (transformers & old motors). None look like yours, and you used it in a way I never considered.
If you want a coil like that, its a standard 120V to 24V (I think) transformer. Some like this one are poorly constructed so the E and I shaped sections are joined with a shallow weld that a grinder can take care of. Better ones, the E and I sections alternate between top and bottom and are glued together - almost impossible to take apart. This coils was from a old APC UPS rated at 1000 to 1500W if I recall. Look in a recycling bin for somthing like that to get one for free :)
@ElectromagneticVideos no, I don't want another. I want to know how to use another. i have no ultimate product in mind, I just want to understand it a bit better. I guess my goal can be to make a rudimentary compass needle. Maybe I should power one, then wave a compass around it to see where the field is... I can use a normal compass like your mag-wand, right?
@@Iowa599 Yes - that mag wand is just a two axis compass! To magentize a plain old needle for a compass, the easiest way is to just stroke it with a strong permanent magnet. Or use one of these: th-cam.com/video/AZsYHLHlIso/w-d-xo.html
@@Iowa599 Sorry - misunderstood. Yes - a compass is a great field detector. Be careful not to get it so close the magent pulls the pointer off its axis though.
Great video again! Regarding this I have a question about motors in my Nagra tape recorders. In these motors the rotor is a coil of wire with no laminations with inside there sits a permanent magnet which is completly enclose by the coil. To replace the ball bearing inside the complete coil and magnet has to be taken out of the housing. This then needs to by kept in a special cylinder (mu-metal?) so the permanent magnet doesn't loose its strenght. Can these Alnico magnets loose there magnetism so quick if it is kept outside of the motor housing? I found this rather strange. Its all in the manual and reads that if its not done like this the motor needs to be send back to the factory in Switserland to be re-magnetised. Sorry I can't show pictures of it here!
That is interesting! So when the rotor is removed, the magnetic circuit - that path that the field flows though now is mostly air rather than metal, which tends to encourage demagnetization (closer to the downward section of the BH hysteresis curve). If subjected to vibration or warmth (more energy to jiggle the domains around) down the curve you go and the field drops. Put it in a cylinder and you once again you complete the magnetic circuit and its much easier for the magnet to stay magnetized. Any reasonably thick iron or steel cylinder (pipe) should do as long as it is only marginally bigger in diameter than the diameter of the rotor. You need a close fit. Bang the rotor while its outside and the magnetism could be gone. So I think that's the manufacturers concern. I'm a bit puzzled by the coil around the rotor. Is it powered to try and boost the field or keep the field at its peak? Or is it some sort of sense coil to provide some sort of feedback such as if the magnet slips out of synchronization with the stator's rotating field?
Some meters have magnetic field sensors that can be used to measure the DC field and hence DC current. Not as accurate close to zero as the transformer action based ones, but still very usable for most applications. They are remarkably inexpensive the days ($50 or so)
In oder to avoid high current, could time also have the same effectivness? (ex. in lieu of a few seconds at 60 amps, then 15 amps over an hour?) An alternative method can be applying electrical current, while heating to luminescence?
It doesnt really accumulate over a length of time. You really need a high strength magnetic field so high current is a must (or many turns). You right about heating - apply current while hot and above the Curie temperature and then cool down while maintaing current. Rocks thats were once hot like on the mid-oceanic rifts become magnetized by the earths field as a natural example of this.
Ha - yes! Are you Canadian too? They are truly the easiest screws to use but sadly they are uncommon in most other countries. The History Guy did a nice video on them if you havnt seen it.
@@ElectromagneticVideos Indeed I am a fellow Canuck. I enjoyed your magnetic to electric circuit analogy. Many years ago, I taught a college course that included AC and DC circuit analysis as well as magnetic circuit analysis - I taught the material exactly as you did. Sadly, magnetic circuit analysis isn't on the radar in many programs.
@@carlosanvito Really? I haven't taught university courses for years - I'm amazed it is being left out. When I was an undergrad, it was in both the 2nd year physics introductory EM course and further elaborated on in the 3rd year EE machines course. We had some of the best profs for both courses - to the extent that I was not expecting to find the machines course very interesting and ended up thoroughly enjoying it.
@@ElectromagneticVideos I was in university a million years ago and at that time fundamental EM was taught to all engineering students in a first year course. That was a great primer for those of us in EE to better understand concepts around transformers and rotating machines that would follow. Communications and Maxwell's laws studies would be highly restrictive without EM basics. My observation is that basics are taking more of a back seat in favour of material which attracts more paying students.
@@carlosanvito I'll bet we were in university at about the same time (give or take a million years :) I have come across that paying student shift - once hired someone from what looked like an excellent community college program . Turned out there was huge disconnect between what they said they taught and what the students learned - turned out the program was 99% percent students from one foreign country and grades were inflated to keep the students coming. I gather at the university level is huge pressure to make the courses "entertaining" at the expense of the fundamentals.
I have already shot it - still need to edit it. I have two vintage de-magnetizers I demo - one a tape bulk eraser and a TV repair loop CRT de-magnetizer - lots of nice colors when that near a the CRT TV in my workshop!
Maybe you could use the primaries from two microwave transformers. They could be offset to each side as you did here. Properly phased you do the entire magnet at once.
70 amps seems very high for a battery charger! Would this current not turn the water to hydrogen and oxygen. What about an arc welder with just a few coils of very thick copper to magnetise.
The charger's high current output is for boosting to start a car with partially charged or dying battery. Its an old one - no fancy electronics. When charging a typical 12V battery it typically puts out about 40A - a bit much but great when you are in a rush. And you right - that amount of current (or less) after a full charged will create hydrogen and oxygen in a lead acid battery. An old style (DC) arc welder would work well too - its natural current limiting ability could be very useful for that sort of thing. Great thing about the old style arc welders is that they are are often available quite cheap in the used market. I got an old 230A vintage AC welder for about $100 a few years ago. The new electronic switch power supply arc welders would certainly have the current generating ability - but I'm not sure how well they would react to being attached to a coil - I wonder of they would determine something is wrong if they dont detect an arc and shut down.
An electromagnet does not need to have a core at all - all you need is a loop (or loops) of wire with current flowing though it and and you have an electromagnet. You could just loop some wire around a piece material you are trying to magnetize, pass a large current though it, and it would work. But you would need a lot of current. If you have a Ferromagnetic material like iron or steel as the core of an electromagnet , it will increase the B field strength considerably beyond the the field without the core. Also, regardless whether the coil is around the magnet to be, or another core, if you can have a complete magnetic circuit out of steel or similar for the B field to flow though, you will get a higher B field up to the saturation limit of the steel and can magnetize with a lower current. For really high strength superconducting magnets, you often don't use a core since the currents are so high the field beyond the saturation limit of iron or steel and the core would have little effect. Hope that helps!
Something I saw years ago....a guy in a shop I worked at had salvaged a coil out of some ballast...even with the iron core removed, it weighed a couple pounds. He wired a momentary contact switch in series with it, and drive it off 120 volts ac. Done just exactly right, you could magnetize and demagnetize with it. It might take several attempts to magnetize something...you had to hit the switch quick, but you could do it. Never tried this myself, but it worked...
Doing it with AC is wild. I guess if you turned it off after the current has reached a peak (ie max H field) and before it reverses your would end up with a nice strong field. So the second half of every half AC current cycle. So maybe 50% of the time you win, 50% of the time you loose. And furthermore, pressing it for a really short duration can result in high inrush current to that is still there when the switch is turned off. How clever!
Thank you so much Emre! Really appreciate your comments. I hope to be uploading more stuff middle of next month. Unfortunately have been too busy with work to do any videos in the last month :(
Explained so clear, so simple and so complete and so interesting ... I'm gonna remagnetize the magnet of my woofer. I think it will work. Thank you for the info, well done ! Greetings from Belgium. PS : Is it possible to DEmagnetize a magnet or something magnetic wich may not be magnetic / might not become magnetic , and if Yes, How ?
I'm glad you found the video simple and clear. A few thoughts: I think the hardest thing will be making a suitably shaped magnet core to fit nicely against the woofer core. Also, try and make the iron in the core you build have a greater cross sectional area that the woofer core, so the magnetic field is squeezed a bit to increase the flux density at the woofer core. And wind lots of turns of wire around the core you make - all along it. And be sure to get the polarity right to so you are adding to whatever remaining magnetism there is in the woofer. There are videos from people who have made magnetizes, so look at them too if you have a chance. I'll bet someone has done woofers. Demagnetizing: Have I got the video for you! th-cam.com/video/mGK8oYdEqyE/w-d-xo.html Greetings from Canada!
Thanks for walking us through the basics. I recreated the magnetism of those horseshoe magnets that are in old phones to make the ringtone, once. I just wound on coarse wire and connected to some series connected car batteries, nothing you should do. - But it worked!
Its really neat how easy it is to make an electromagnet. Course wire works fine - and for any wore, the more turns the better. One caution for anyone reading this - car batteries can deliver so much current the can be a bit dangerous for this sort of thing, but a few plain old household D batteries are usually enough!
@@ElectromagneticVideos I believe while magnet is hot (and cooling) or if the metal is repeatedly and firmly tapped while still in the wire coils it can pick up some permanent magnetism like you shown.
THANKS FOR ANOTHER GREAT VIDEO!!! Between timestamps about 9:10 to 9:15 while you were talking about the 'magnet resistor', the word "RELUCTOR" popped into my head! Also, have you heard that they were (for a while) actually selling school magnets with "N" and "S" REVERSED!! It had something to do with the fact that teach that a magnetic compass will always 'point north' so that the compass will demonstrate that earth north will actually be demonstrated....I think they stopped this nonsense. I got a few of those pole indicators, like you shoe at about 11:10 One was actually hand labeled "Green = North" (none of the others)?? I ignored this. One more thing: When you were REmagniting a material why doesn't the alternating, AC, magnetic field just push and pull the domains, leaving no net effect. THANKS AGAIN....still catching up on your fantastic videos! Please keep them coming. --dALE
Thanks! Glad you enjoyed it! I just googled "reluctor" - seems to be a sensor type commonly used in cars for crankshaft position based on magnetic reluctance - how interesting! I had never heard of magnets being mislabeled the wrong way for "educational" reasons, but doesn't surprise me! Still strange! Remagentizing - did I accidentally imply I was using AC? If so, it should have been DC. I have heard of people using AC which works if you turn off the current close to the peak of the cycle. You then have a 50 % change the magnet is magnetized one way or the other. Apparently do it a few times testing the magnet in between and it eventually works. More videos coming - if you havnt seen the "Measure the speed of light" video, take a look. I'm working on the DIY followup for it.
@@ElectromagneticVideos Yes, I have seen the "Measure the speed of light". Remember, we had a brief discussion on modulating HeNe's?? BTW: What's your first name...may help getting acquainted for TH-cam.
@@ElectromagneticVideosI just re-watched the video. I assumed AC since it was a transformer core. I guess you did, indeed, indicate the current was DC when you applied power with a battery charger. AND when you used the B-Field checker....sorry --dalE
@@dalenassar9152 No worries! Its funny - I am always amazed at how I misspeak when doing videos so I would not have been surprised if I had got it wrong! I think in normal conversation we make more errors than we realize, but not being recorded they are so fleeting they don't get noticed. You wouldn't believe the amount of editing or re-shooting video I do to correct what I say!
@@dalenassar9152 Strangely I just saw your "Yes, I have seen the "Measure the speed of light". Remember, we had a brief discussion on modulating HeNe's?? BTW: What's your first name...may help getting acquainted for TH-cam." comment - it was quarantined for review!?!?!? TH-cam seems to sometimes get confused about what good and bad. Yes - I remember we had that discussion - sometimes when lot of comments come in its hard to remember who I had what discussion with and there does not seem to be and easy way to see what discussions I have had with anyone in a different video. BTW - I tried once to change my comment name to "Pete @ ElectromagneticVideos" but was unsuccessful. Will have to try again!
Very nice video. I use a very strong neodymium magnet rated at 600 hundred pounds of pull, I don't know how much gauss it produces, I don't have a gauss meter to check it. I do use the neodymium to recharge my alnico magnets and does make them strong again, I'm sure it's not full saturation, but they are strong again.
Thanks! That's really neat to have used one permanent magnet to charge another - makes sense with a strong neodymium magnet. Do you have anything like shaped piece of iron to guide the flux from one magnet to the other and compress the flux into a smaller area to raise the density closer to the saturation point? Thats really what would would have liked to have for the demo I did. By the way - great vintage videos you posted of electrical demos! Just subscribed so I can watch the later!
@ElectromagneticVideos Thank you for subscribing, I will be posting more later. To answer your question, I just touch the neodymium magnet directly on the Alnico magnet, North pole to South of the neodymium, and then turn them around and repeat the process.
Very nice video, Sir, however i have a question regarding this video. In this video you talk about high current and moderately low voltages. From a welding machine i guess 48 Volts. On another video thats called 'MAGNETS how its Made' from Discovery UK they say that in the first step (high current/low voltage) they prepare the magnets for establishing the polarity, then in the second step they use High Voltage, low Current to really magnetise a magnet, (in that movie 30 Amps x 300+ Volts). So i am a bit confused now. Can you clearify this. Thanks.
Thanks! I tried looking for the video you mention but couldn't find it it so I will make some assumptions about what they are doing. You mention that they initially using high current/low voltage to prepare the magnets. Are the magnets hot or even molten at this stage? It might be to try and orient the domains or crystals as the material cools in a way that is optimum for the a magnet with with fields in the desired direction. I'm guessing only a small number of loops in the current carrying wire. 2nd step: HV, low current 30A 300V. For the final magnetizing step you need to force a field somewhat above the saturation level of the material. The H field that does this depends on the Amp-Turns of the coil, so you need a minimum number of amp turns. You can have a few turns with high current (eg 10 turns at 1000A = 10000 Amp turns) or many turns at lower current (eg 333 turns at 30A = about 1000 Amp turns) . How you get the required number of amp turns doesn't matter and would be chosen based on what is easiest to wind given the geometry of the magnet and the easy availability of suitable power supplies. The voltage that is needed is determined by the total resistance of the wire. More turns = longer, usually thinner wire so more voltage is needed for a given current, which is partially offset by the need for less current. Bottom line - they used many turns to need less current and used high voltage to push that current through a thin, long wire. I used a few turns of thick wire. I probably didnt mention the alternate option of many turns and lower current - often the videos have to be kept somewhat simplified to avoid confusing or complicating the concepts being presented. Hope thats helpful!
@@ElectromagneticVideos Thank you very much for this great and fast reply, i really appreciate it. I am trying to magnetise U-shaped O1 tool steel that is hardened and tempered. For the magnetisation i use a welding machine as power supply (48v AC), then a bridge rectifier to make DC. That DC is connected to the primairy (thick) winding of a microwave transformer, so +/- 3 Ohm. When i magnetise this U shaped tool steel i can not get higher then around 30 Gauss. So i thought i go check online and found this video. th-cam.com/video/qed4ynPYVIA/w-d-xo.html So that leaves me with 2 more questions if you don't mind. 1. Is there a way to find the magnetic saturation level of this hardened and tempered O1 tool steel? and 2. Would the tempering proces (in my case 2 times 2 hours of +/-200 degrees Celcius heating, then slowly cooling) have an effect on the magnetisation level? Anyway, thanks for the effort and happy new year.
@@germona Interestingly I geographically blocked from that video! Your questions: 1) The saturation level for most steels is between 1T and 2T. If you estimated the current needed for 2T you are almost guaranteed to be fine. If you can measure the B field, and do a few readings for different currents, it should be obvious when you have reached a current level where the field does not get much stronger. There is a nice graph here: en.wikipedia.org/wiki/Saturation_(magnetic) 2) I'm not sure how the tempering process would affect the magnetization level that can be achieved - I would think it will affect the magnetic hardness hardness (how easy/hard it is to loose the field after magnetization) because the crystals and stresses in the material will alter how easy it is for the magnetic domains to change. I'm not sure if tempering - or cooling the steel quickly will make it better or worse. I'm sure somewhere on the internet there is some practical info on that. (let me know if you find out!) In general "normal" steel as found in tools does not make great magnets as it is magnetically soft so it will generally make magnets that easily loose their strength which is why other materials are usually used to make magnets. Depending on what you are trying to achieve, you might find you get better results is you use a alnico or neodymium magnet of about or bit more than the cross-sectional area of your piece of steal and use the your steel to guide the field to where you need it. If you are just experimenting to see how to make magnet, keep experimenting. I did have a large steel horseshoe magnet as a kit - it worked - but was never very strong and quite weak compared to what we are used to today.
@@ElectromagneticVideos Thank you again. I am trying to make a horse-shoe guitar pickup, like in the rickenbacher frying pan A24 lap steel guitar, that was invented by George Beauchamp in 1932. It is not very much magnetic but a little more then i can get now. If you search in your browser for images on 'horseshoe pickup lap steel' you will see a lot of examples. I have a rickenbacher lapsteel from 1946, and that magnetisme is still there, and that is the amount of magnetisme that i am trying to archieve. I will keep on trying. Thank you for the help. Jean Belgium.
@@germona You know, someone else asked about that a while ago. Did a bit of googling and I now see what you are dealing with. At least one video I looked ta did seem to indicate after recharging the magnet the most yo could hope for is a year or so of use before needing to repeat the process. Here are some thoughts: I did some research on annealing steel and magnetism. Annealing can increase steel's magnetic permeability (higher field for a given current) but decrease magnetic hardness (easier for the magnet to loose its strength). So it would seem steels that have not been annealed generally make better permanent magnets. I am wondering if over many years the steel gradually undergoes similar changes - reduction in internal stresses - as when it is annealed and so that what was a good steel for a permanent magnet when the guitar was made is no longer that good for a magnet. Some thoughts - you could try heating the steel to almost red hot and then rapidly cooling it to harden it which might help. However I would be hesitant to do that on an antique item like you have and presumably like me. you have little experience doing that sort of thing. I did see one fellow who re-magnetized it by swiping a string magnet along it. You could try that and maybe swipe it with a magnet before each use. Even better, is there some place underneath where you could glue one or more strong magnets to the old horseshoe magnet? That would keep it permanently charged and might be the simplest solution. Let me know if you find out what works best. Good luck - what an interestg project!
I am the first time to see your videos. It is very well executed and explained clearly. I wonder what your current supply look like. Thanks again for your wonderful video.
Thank you so much! I am gradually learning how to do these videos and I think they have gradually gotten better as I do more of them. It has been great fun because they have given me an excuse to do many ofthee things that I haven't done since I was a student!
@@manla8397 I don't have a photo of it right now, but it is an old analog automotive 12V battery charger that can put out 100A or more to also help start the car. You really need the old analog style ones for this because the new switching power supply ones will do all sorts of things and detect its not a battery and turn off. You can also use a variac to control the output of the old style charger. You could also use an old style arc welder controlled by a variac. If its an AC welder you can get a 200A bridge rectifier to make DC.
Definitely more intrigued to learn about electro magnetism and more of physics as a whole I never payed attention in class unfortunately but science and math where always interesting topics. Nice video thanks for the simple explanations
Thanks! That's exactly what I am trying to do with this channel - make those interesting things understandable without the significant science and math background normally needed. More videos in the works!
When I was a kid that always fascinated me. I remember reading about it in some National Geographic article (probably from the '50s or 60s - my dad had a huge collection of NGs) I think about showing the spreading of the sea floor around mid-oceanic ridges.
@@gfr2023 You know, now that you mention that, I do remember reading about that too. I think they were able to get the date of the fire pretty accurately from the direction of the captured magnetic field and knowing where the north pole was at different times - and that maybe from the mid-ocean rift data.
Perfect video that I was searching for long time, but I have a question :- can you make another video to explain the side by side (magnetic N = bottom of metal, magnetic S = top of metal) + thks ❤
Thanks! I quite understand what you are referring to. Could point to the point in time of the video and try and describe the question a bit differently?
Hello, are you thinking of doing a course on these topics (Electromagnetism and Electrical Machines?), I mean, because electromagnetic circuits and Gauss Equations are not exactly topics of general culture jajajja, take care and good luck with your channel.
Sort of. What I am trying to do is bridge the gap between the mathematical treatment of electromagnetics etc as done in typical university level courses and the handwaving descriptions used elsewhere. I have been occasionally showing things like Faraday's or Ampere's and saying things like the first part of equation is the curl - think of it saying if there is a circulating field like a whirlpool ... . So I hope to give those without a rigorous EM background a sense of how things work, and those with the math, a sense of how it applies to practical things. I don't plan on give an online course on EM since thats been done a million times before :) At some point I might do a more organized series of videos to create a pseudo course though.
We used to magnetize screwdrivers with a car battery and a piece of stranded copperwire wrapped around the screwdriver. the more turns the better ,, then we would short the 12 volt batter leds across positive and negative till the wires were smoking then after lettting it cool off we had amagnetized screwdriver which was way stronger than the pocket ones . Automotive hacks fro picking up screws ect out of intakes or disributors back in those days .You have made a few comments in regards to heating up the metals to line up the direction of the north and south poles in the structure of the atoms inside the iron. This is how the majority of ferrite and neomydium magnets are made in the industry . However certain metarials added will increase the feild strength as well as be subject to the breakdown polarization of the atomic structure inside the magnet it self. . most applications as far as the hobbiests will ever use themm for do not go beyond 100 degrees f.. however certain kinds made for the Areospace and space industry have higher breakdown temps due to thier conditions in outerspace. Have fun in creating your own magnets. I tried a dc welder the other day to try to magnetise an iron nail.. i couldnt hold the wire feed long enough on the wires to create a long enough field . tommorow i will try heating the nail first and using more wrapps around the nail and then quench it in cold water to see if it will retain the magnetic field. ty for your basic presentation of the magnetic theory. the coils setup that you made i had completly forgotten about .. I have always been into magnetic induction and fields ect since i was a teenager. im 61 now and retired and have nothing but free time to enjoy this one of many favorite hobbies of mine.
I have heard of variation of what you described. I guess the trick is to do it just long enough but not so long that the wire melt from all the current available from the battery?
@@ElectromagneticVideos yeah that s the idea,, fine wired cabling works better than solid core ,as in house wiring though it will work.. just need alot more turns ,and fry your battery too.. better to use stranded wire as it carries more current ,, i have melted down wires before and they do have a tendacy to catch on fire ,,so beware .
@@randallmarsh446 " i have melted down wires before and they do have a tendacy to catch on fire ,,so beware" Yes! Might not be a bad idea to make a "fuse" with a length of slightly thinner wire to protect the bigger wire and battery...
Just so its clear, if you have a really strong field to charge the magnet with, no need to tap, but if the field doesn't create saturation in the magnet being charged, tapping can provide a bit of energy to help the domain boundaries move. Also, not sure of how well it was shown in the video, but magnets are often brittle and if you tap them too hard bits can break off.
Very nicely put but I still in my own right think that the domains are really nothing more than the attom of certain metals having more free electrons which creates a higher covalant bonding and the north and south characteristics are because of the manipulation of electrons making up the negative magnetic pole realative to the stationary protons the positive magnetic pole.
Here's the thing: if you have theory for magnetics or anything else that you believe is better than the existing ones, you have to demonstrate it by showing: a) that it correctly predicts what the current theory predicts correctly b) that it correctly predicts some things that current theory gets wrong (ie current theory has a flaw that can be shown by an experiment yet your new theory does correctly predict the result. ) Part a) confirms that it is at least as good as existing theory Part b) shows that it adds something of value in addition to existing theory. If you have both, you may have a winner! With Classical Electromagnetics, achieving the above is not easy - the existing theory correctly predicts so many things so well, and its main missing points are filled in quite nicely with Relativity and Quantum Mechanics. So the challenge to you is, make a youtube video explaining your theory and also demonstrates with an experiment how it fixes some error in what the existing theory predicts.
@ElectromagneticVideos Yes, my comment on your demagnitizing video acknowledges that. But now I have to unsubscribe because you are taking my comments as an insult rather than what they were intended for. I was merely trying to have an open-minded conversation to stimulate and motivate critical thinking. Have a nice life.
It was a 12V battery charger with a high/low setting so probably between 15 to 20V. Since the resistance of the coil is really low it really didnt need much of a voltage to drive that much current.
If you mean whne you are magnetizing it, no - assuming you are are already subjecting it to a good strong field. Howevern, once magnetized, there are a few things you can do to keep it nicly magnetized: 1) Put a steel bar or similar between the poles to make it "easier" for the B field to stay high on the BH curve 2) Dont subject the magnet to vibrations or shock 3) Keep it cool 4) Dont force it near an opposing magnetic field. What I did leave out is all of this depends on the material the magnet is made out if some - some are more or less vulnerable to any of the items listed above.
I must be asking something already addressed. Sorry. But, for the transformer, did you remove both the primary and secondary and not modify them at all? Last question, in this video you connect the input terminals of the primary to your 240 volts AC wall outlet and you did not connect the secondary terminals to anything. Correct?
@@ga28282 The transformer is an auto-transformer - it has a winding with a tap on it. For these purposes it doesn't matter. What does matter is the number of turns on the coil and the thickness of the wire. To magnetize something, we dont use AC - we use DC. I am using a an old style car battery charger that produces about 20V DC or so at up to 100A depending on the resistance of what it is connected to. So the thicker the transformer coil, the less resistance. Measure the resistance with a voltmeter and you can determine the DC current that will flow for a given voltage which will be much more than the AC current the transformer normally carries. In my case the AC transformer would have been rated at 120V at 8A for a few minutes. As you saw I could push 70A DC though it (but only briefly since I dont want the winding to burn up with all that current). We want to maximize the magnetic field which is determined by Amp-turns - the current times the number of turns. For a surplus transformer with a 120V or 240V primary, usually the primary is the coil to use. Try it at a DC voltage of 5 to 10% of the rated AC voltage. If the DC current is more than the rated AC current, OK to do it for a few seconds - but be careful not to overheat the coil. Hope that makes sense!
Oh - you can put the secondary in series for a bit more field - assuming you can figure out its correct connection to increase rather than decrease the field. If is a 10:1 transformer you would get 10% more amp turns which may not be worth the effort!
@@ElectromagneticVideos I will take a look. Thank you. I have a 0-30 volts DC power supply that does up to 10 amps. We'll see what happens. Thanks I learned plenty from you
I have a magnetic implant, a neodymium magnet 2mm by 1mm, its inside my finger but over the years has lost its power, any ideas of how I can re-magnetise it without burning or electrocuting myself???
Obviously, I cant provide any medical advice. To re-magnetize a magnet, you need to subject it to an intense magnetic field, which will also STRONGLY pull magnet. I would be really concerned about about that causing all sorts of damage, possibly ripping the magnet right out of your finger, and maybe in the worst direction possible. So I sure wouldn't risk anything like that. Sorry ... not the response you probably were looking for.
That a good question and one which I don't know the answer! But its not very long - a fraction of second depending on the material. Its essentially the same mechanism to magnetize an electromagnet into saturation and transformers can go into saturation well beyond standard AC frequencies of 50 or 60Hz. I know people use charged capacitors to very briefly push an enormous amount of current though a coil to magnetize magnets and that would also probably in the fractions of a second. If anyone has any experience charging magnets using a capacitor, would be great to hear how long!
@@ElectromagneticVideos That's what I plan to do. A big HV capacitor. Few thick copper wire coil. A fast high Current high Voltage switch (Thyristor) That's all, very SIMPLE.
@@paulcohen1555 Perfect! If you do it I hope you make a video - I would be interested to see how it turns out. One thought - you don't need giant thick wire. Something like household wiring wire can do hundreds or thousands of amps as long as it is only a fraction of second. You may have to experiment with how many turns is optimal. If you are using HV more turns will be better. If you have scope clip the probes on the ground end of the wire you are using with only a few inches of wire between the two scope clips. The wire will be like a really low Ohm resistor and you can watch the current decay but also see its peak value.
You could, but to get the same level of B field (ie to saturation) with a similar current, you would still need and iron path connecting the two ends of the magnet together to make it easier for flux to flow.
If I am understanding you properly, a large, steel, C clamp whose frame was wrapped with an electrified coil of doorbell wire would be perfect for magnetizing a bolt or a nail and making them permanent magnets.
I never thought of a C clamp for that but - YES - great idea! You would want the metal in the clamp to be thicker than the magnet (so at its saturation point there is more than enough flux to saturate the magnet-to-be) and also the have the magetic path though the clamp as short as possible (so smallest clamp). This would minimize the amp-turns needed. The only issue with a bolt or nail is generally they are not ideal materials and tend to be vulnerable to easily loose their magnetisim with the slightest misuse.
@@ElectromagneticVideos Thank you. My thought is to take a rotary hammer SDS point bit (primarily made of carbon steel, normally used for smashing stone) that has lost it's point through over use, grind the point area flat, heat treat and temper it, then put the new flat flat end in a C clamp as described, magnetize that end and use it to hold nails as the rotary hammer hammers the back end in thereby driving nails with a rotary hammer. Just something to do while bored.
@@ElectromagneticVideos I have an old C clamp I made in shop class a few decades ago out of heavy steel with a steel frame about an inch and a half thick in all iirections. Should be perfect for the task.
@@kenibnanak5554 Your Welcome! Thats a neat idea - I would be vey interested to hear how well it works. The concern I would have is the violent hammering action on the bit by the rotary hammer + the open magnetic circuit on non-ideal magnetic material would rapidly demagnetize the bit. The tempering may help make the material magentically harder (I'm not 100% sure) and retain the magentism better. If you find it does loose its magetism after some hammer action, one option may be to mount a magnet very near the bit close tot he chuck. Would be tricky to get it gear enough without touching - maybe a held with a thick piece fo steel with a bolt into the threaded hole where the side handles often screw. Anyway - go for it! Should be interesting and potentially really useful.
I dont know about it in particular, but most steels are. There are steels like silicon steel that are designed for specific magnetic and electrical properties.
Learned a lot. Thanks. Doesnt a type of welding-iron uses the principe with the curie-point ? And that don't seem to be "dangerous" for the magnet. (And a trivia: In swedish BH is the same as bra.... :) )
Your welcome! Not sure what you mean with the iron in terms of the curie point. If you elaborate it might help. I think your referring to what I would call a soldering iron which melts a tin+something (lead in the old days) to attach electrical wires or devices. The alloy is not normally a magnetic material so it no risk of magnetizing it. Most soldering irons operate by a resistive element providing the heat and with little current flowing there is little magnetic field. Solding guns however use a transformer to create large current to heat the tip and there is a huge field as shown here th-cam.com/video/mGK8oYdEqyE/w-d-xo.htmlsi=heddjVD9ww3PlMmJ&t=537 . So that could demagnetize nearby magnets. Trivia - I'll bet that is the source of endless amusement in introductory electricity and magnetics classes in university :)
It doesn't need to be touching, but the larger the gap is, the lower the magnetic field from the electromagnet will be and so the effectiveness of the magnetizing process will be reduced. As long as field is somewhat greater than saturation value of the permanent magnets material it should work fine, just this will be harder to achieve with a bigger gap.
@@ElectromagneticVideos Thanks, I appreciate it highly say for arguments sake you passed a permanent magnet through an electromagnetic field indefinitely in and out of the field would it then holds its charge forever in theory?
@@helpyousleep8173 I'm not sure what you mean by "passed a permanent magnet through an electromagnetic field indefinitely in and out of the field". Bottom line: if you have a good magnetically hard material for your magnet and expose it to a nice strong field (above its saturation level) to charge it, it will hold its magnetism well. However, do "bad" things to it like forcing the like poles of two magnets together, and maybe even banging them at the same time, and the magnetism will be reduced or lost.
@@helpyousleep8173 If the want a general electromagentics text book, Electromagnetics by John D. Kraus is the one to get. It covers all the theory and includes applications. But you will need some math background, most importantly vector calculus. From your questions it sounds like you are more in need on something specifically dealing with magnets and some very hands on advice on making them. I dont know of any specific book that covers the the very practical aspects of making magnets more from a production and manufacturing process. So unfortunately the best advice I can give is google or go to a university library, or even better better, a university Electrical Engineering library or Physics Library and browse the appropriate section. You know, even searching TH-cam might bring up what you are looking for.
Why permanent magnetic fields are not source of electricity??? What happened if we use a negative terminal as earth and potential difference between high magnetic fields and equivalent negative impact by earthing??
To make sure we are understanding each other you mean slide the magnet to the left so the right side of the magnet is now over center leg of the old transformer core, right? That probably would have worked but would have also applied a small reverse field over the shifted left side of the magnet which (depending on strength of that field) might have had small demagnetizing effect on the left side of the magnet. The real issue is that the permanent magnet I used was to big. Ideally its ends would be the same distance apart as the two left legs of the old transformer core. And for that matter one really needs just a U shaped core for the electromagnet as opposed to the E shaped transformer core.
I did something to a magnet, destroyed it with a stronger magnet somehow, but don't know how too explain it. Well I guess I do.. I was pushing a smaller magnet against a larger neodymium magnet, opposing, and the little one just gave out all of a sudden. No more magnet.
Thats too bad - but not uncommon. When you push the same poles of two magnets together, the fields try and shift the domains in the other direction. Do it a little and you manage to move some of the domains such that the field is diminished. Do it with a really strong magnet and you can magnetize the smaller on in the opposite direction but its hard to get the field strong enough to do that. So in your case the big magnet managed to reverse the domains at least party in the smaller one reducing its field.
Basically a magnet is a trapped polar charge. And any magnet in any form is in fact a permanent scalar wave emitter. If a single coil with sufficient length of wire will pas through permanent magnets and magnets are placed at a distance equal to 1/2 of wave length corresponding to frequency of the alternating current voltage will will be greatly amplified while ohmic resistance in wire will be reduced by 95%. The higher the frequency the shorter distance between magnets where they MUST be placed exact where 1/2 of wave length is (max amplitude) This a different way to exploit permanent magnet effect and not only 200 years old methods … ie Faraday, Lentz Manipulate magnetic field to create electricity or manipulate electric field to create magnetic field/flux Remember, two separate electron flow running against each other create scalar waves, zero point energy or whatever name scientists use for this effect. And all this is possible because existence of aether … Galileo Galilei said: E pur si muove ! Magnetic field means instant action at distance … instant is obviously faster than speed of light, yet mainstream science deny it against all evidence !
8:48. Why bother with a steel core? Couldn't one simply wrap a coil on the magnet? Run a current through coil and maybe tap the magnet to jostle any remaining stuck domains into alignment with the applied field? Then you went into magnetic circuits and the resistor analogy. The seperate C shaped iron core represent a low reluctance path which helps complete the magnetic circuit with a low reluctance path which allows (creates) a stronger magnetic field throughout the magnetic circuit than if there were more high reluctance paths in the magnetic circuit.
The second half of you comment is why - the low reluctance C minimizes the amount of current (or more accuratly amp-turns) needed to achive the required field in the material you are magnetizing. You could certainly do it without the C exactly as you describe - just more turns of the coil and more current. In the end it just depends on what is easier.
@@ElectromagneticVideos I'm sorry I may have worded my inital comment a slightly differently than I intended it to be understud. The first half was a question I had, and the second half was me figuring out why use a core for magnetizing after you gave a simple magnetic circuit analogy analysis. 😁 A question asked and auto-answered.
Not quite sure what you mean. Reluctance circuits are a pretty standard way of approximately calculating magnetic fields in this sort of situation. Here is a link a that describes it in a bit more detail: eepower.com/technical-articles/magnetic-circuit-properties-understanding-reluctance/#
I guess I goofed on that one :) 16th would have been better. I find its surprising how many times I say things like when thinking out loud while videoing. I suspect we do it all the time in normal conversation just there isnt the playback to make is so obvious!
@@hongkongkong7174 It is! And a bit shocking how many inaccuracies pop up when I edit the videos - you wouldn't believe how much I have to correct when editing. I guess that's why the pros use scripts!
ok i have an old permanent magnet generator from the 1974 its 1800 watts it was my dads. it was handed down to me.. It sat in storage for years . when i got it and started it up it only did 800 watts i thought ok 800 watts i shut it down .. the next day i started it to show my friend it then made the 1800 watts???? i guess I'm picking your brain lol... my friend says the magnets had just rejuvenated... is that what happened?
That's really interesting! So assuming its AC, there are some interesting behaviors that are associated with AC motors and generators. If you have an inductive load attached to the generator (like a typical AC induction motor) the field created in the generator from the lagging current flowing to the load will tend to oppose the magnetic field in the field magnets and potentially try to demagentize it. A capacitive load (rare) will draw a leading current and tend to strengthen the field. Maybe there is a capacitor in the generator to encourage that, although I have never heard of that being done in a permanent magnet generator. Its typically done for induction generators. Another possibility is a series field winding to strengthen the field when more current is drawn (simple voltage regulation) . Thats typical of electromagnet field windings but could be done in permanent magnet ones I suppose. Of course with all of that said it could be something simpler: Are there brushes/slip rings? Could it be they got cleaned up after a bit of use? Or maybe some connection was poor and heated up and fixed itself? Has your friend seen magnets get rejuvenated before in a generator? If so thats really interesting - I'm an EE but haven't done much with motors/generators since university. How did you test the wattage? What type of loads?
@@ElectromagneticVideos stuck a really powerful magnet to the side of a metal bucket. Filled bucket with water. Heat piece of metal in a forge to above it's curie point. Quickly quench the hot metal close to the magnet in the bucket... and Bob's your uncle.
in reference to demanetizing an object, grandpa showed us that you could use a spark plug wire to zap what ever you wanted to demagnetize by allowing a spark plug off the engine to arc across the object a few times.. but wear gloves when you do this engine coils are extremly unforgiving1and use a pair of no elctrical holding devives such as a plastic tong from the kitchen an not a pair of plastic coated needle nose plyers..haha
Interesting that a spark plug type zap would do it since the current isn't generally that high. I wouldn't trust the plastic on pliers or gloves for that types of voltage - an yes - I have been zapped before :)
@@ElectromagneticVideos Do ALL magnets loose some magnetism over time? Even neodymium? What if never used? Can a magnetic domain spontaneously move out of alignment?
@@MrSummitville Thats a very interesting question, particularity since we have have only been making magnets for the last few hundred years. Iron containing rocks that have been heated have retained traces of the earths magnetic filed for thousands (millions?) of years, but those remnant fields are very weak. So magnetism can last a long time. Magnet life is a probability thing: how strongly the domain boundaries are "locked" into place (based on the nature of the material the magnet is made of) and what forces/energy is available to help knock those boudaries loose so they can settle in a lower energy (lower total magnetism) state. We constantly have thermal energy jiggling the domain walls with the occasional random big jiggle being enough to shift/release the weakest boundaries and therefor weakening the magnet. But after a short time all those weakest boundaries are moved and magnets tens to stabilize. Exposing a magnet to an opposing (repulsive) field provides more push to move those boundaries to reduce energy and reduce field so the thermal jiggling can now move some slightly better secured magnetic domain walls. Bottom line: if the random max thermal "banging" of the magnetic domain walls + an opposing field exceeds how tightly the weakest magnetic domain walls are secured in place, the some domain walls will move and weaken the magnet. In most controlled situations - not exceeding a certain temperature, vibration and opposing magnetic field, the magnetism will settle at a reasonable value (which can be very high as in neodymium example). A good example of this is magnets in an electric motor or loudspeaker in a car - very unfavourable place for a magnet but modern ones with materials designed for that do well. So in the end after first magnetizing a magnet, its field will drop a bit but hopefully settle at a (good) level dictated by the environment it is subjected to or operated in.
If you mean whne you are magnetizing it, no - assuming you are are already subjecting it to a good strong field. Howevern, once magnetized, there are a few things you can do to keep it nicly magnetized: 1) Put a steel bar or similar between the poles to make it "easier" for the B field to stay high on the BH curve 2) Dont subject the magnet to vibrations or shock 3) Keep it cool 4) Dont force it near an opposing magnetic field. What I did leave out is all of this depends on the material the magnet is made out if some - some are more or less vulnerable to any of the items listed above.
Nice point when you mentioned the toughness of a magnet through the BH curve.
I've never thought of that like this before.
This type of looking at things means a lot to me.
Thank you very much for sharing your passion with us.
So glad you found a different perspective on that aspects of magnets. I always find hearing a differernt way of looking at something tends to add depth to ones understanding, whether or not one fully agrees with the other perspective.
I am having great fun shareing this stuff - it has been a great excuse to do someexperiments I havngt done since I was a kid or university student!
I finally broke down 2.5 Watt speakers from 1968 since the cones were extremely dried out by weathering and the magnets around the speaker cone still are strong. Ferrite magnets remain polarized by weathering if temperatures never got hot enough to unalign those magnetized dipoles that were originally locked in place. For nearly 60 years Ferrite magnets remain strong.
What an interesting data point on the longevity of ferrite magnets! I wonder how well modern Neodymium magnets will have held up in 60 years from now!?
OVER 6O years. FERRITE MAGNETS ARE MUCH OLDER Than neodymium magnets!!! Black 🖤 FERRITE MAGNETS go back over 1000 years.
I never understood what Amp Turn is, now I do :-) Thanks for basics.
I so glad it was understandable! I just looked at your channel - and the HP 41CX. I'll make some comments there!
the higher the tensile strength,,, basicly the hardness of the steel the harder it is to magnetize ,,such as the difference between a 16 penny nail vs a knife blade made from carbonised steel ..however there are certain conditions you can magnetize high grade steel if you heat the metal up to a glowing red and then keep a current or magnetic feild around the piece being magnetised long enough till the metall cools down it will hold a magnetic field longer and be strongr also. this a basic way of how neomydium magnets are formed ,,If you will watch how magnets are made on an industrial scale you will notice that they will heat the object that is being magnetised , is they will heat t he metal red hot and then will zap it with a similar setup that this video has shown for a few seconds with low voltage and high amperage.. after the metal cools they will zap it once more with around 30 or 40 amps and around 30 volts .. in the final stage. i have been wanting to try this with common metal materials i have laying around such as transformer cores , which is made from highly magnetic material in A/C transformers. A/C current will create a stronger magnet such as used in junkyard cranes because A/C current when turned off th emetal is returned to nuetral if they used DC current in those magnets i the junkyards then they would not be able to release the junk iron they pick up. A/C current creates a very very strong magnetic field although. but is used only in certain applications. to demaganitize a piece of metal then u use a/c currrent .
A nice discussion on magnets. I work with engineering loudspeakers and most of what you said is spot on. I think some of the permanent magnets have a higher B value, but you were speaking in generalities. Did you hear me saying that's not a steel magnet! It's a ferrite. Greetings from near Ottawa!
Mark
Thanks! Steel - ferrite - oops! I find I say a lot of things wrong when making videos and dont always catch them in editing. Must have done it again.
Greetings from near Carleton Place! I see your even nearer to me than Ottawa!
Found your videos very informative and it is surprising you don't have much more views
Thank you so much! I'm gradually getting more views. The are about half a dozen of my videos that have done well with 100k or more views each. Sometimes it takes TH-cam weeks or months to fugure out who to show my thumbnails to and then suddenly a video takes off. Also becomes easier over time. I wish I could predect which videos would get popular but it seems to be almosgt random. I didnt expect the 75 Ohm TV cable (transmission line and reflections) to be popular - best response so far so you never know!
When I was in elementary school, the science teacher hung an iron rod om strings from the ceiling, oriented north south...after a few months, it was weakly magnetized ( could pick up a few pins)..
Two jobs ago, we had a magnetizer/demagnetizer. It was just a coil driven by 120VAC. Just push the button briefly to magnetize, hold it down and slowly withdraw the screwdriver to demagnetize it.
Your videos should be shown in schools!
Thanks! I had not heard of the experiment you described. It must be that with magnetically soft iron or steel the domains are so easily changeable that the thermal energy in a conformable room is enough to gradually change the magnetic orientation. I will have to try that sometime, maybe with a piece of rebar.
The one I remember from grade school is stroking a nail with a magnet to produce a weak magnet. I guess each school and science teacher had a preferred experiment.
Demagnetizers - 10 years ago I was involved in some factory automation design sorting some small items the size of finishing nails. Problem was they would get magnetized. The company's solution - which I duplicated - was to take out the rotor from an induction motor and power the stator with 12 to 24V AC and slide a plastic jar of the items being processed though it. Worked perfectly!
@@ElectromagneticVideos As I understood it, the iron rod was magnetized by the earth's magnetic field, which is why it had to face north south..well, magnetic north and south.
I remember reading an article that steel ships can become weakly magnetized over time...and this can cause navigation problems....at least before gps was a thing.
The " Philadelphia Experiment" conspiracy theory about making ships " invisible" got its start from an experiment to degauss ships, making them " invisible" to magnetic mines...
@@scottthomas3792 There was a faster version of the experiment you describe - same idea but hitting the rod with a hammer to encourage the domains to re-arrange to the direction of the field. I never thought about the steel in ships - but makes sense. When I was a kid we had an compass stuck on the dashboard of my dads car. It had little adjustable magnets you could adjust to zero out the field from the car's steel. We never got it even close to perfect!
I didnt know that was the back story to the " Philadelphia Experiment" conspiracy theory. Shows you how adding secrecy to something like that makes peoples imaginations run wild!
Wish I had seen this much earlier. I adjust the strength of magnets for and industrial application. We don't use an iron core with the coil. The material to be magnetized is the core. There is no need to have an extended time to magnetize the material, so for the current required, a capacitor is charged and then discharged into the coil. Since the magnet is centered in the coil, it is a one step process. When loudspeakers are made, the magnetic material is not magnetized until the speaker basket and magnet assembly is assembled. It is then magnetized. Look for videos of the process online.
So you just use the working coil of the device to do the magnetization - with huge burst of current from a capcitor - what a greast way to simplify the process.
I had no idea speaker were magnetized like that. I'm amazed that the fine wires in the coil can take the current - but as in your example - a brief burst is all it takes. I guess for the same reason, not enough energy in the current spike to move the coil enough to damage it.
@@ElectromagneticVideos They don't put the current into the voice coil. The magnet assemby is inserted into a larger external coil with high current capacity. The coil I use at work can fit a 4X6 piece, up to 8 inches long inside the coil. The coil is from a 30 KVA power transformer. The winding is 6AWG. I'll have to look at the capacitor value at work. I do remember it is rated for 63 working volts. I think it is 33000 MFD. The entire cycle is over in about 200mS.
@@isettech Oh - ok - that makes a lot of sense. Thanks so much for the details. I may try an make a magnetizer like that someday!
came here after you sent me from another video haha. you do a great job of making it digestible you are an excellent teacher sir
Thank you so much! Glad I sent you to s video you liked!
Another way, maybe better, is to charge a suitable capacitor and dead short it against the magnet coil. With some care, from the B and H diagram one can obtain the (co)energy density of the magnet metal per gram or cc and calculate the total magnetization energy required by the magnet in Joules. Then using a generous safety factor let that be the capacitor energy before the short
It would probably be better - certainly could be done with a much smaller power supply. And your absolutely right - do a calculation as to how much energy is needed and setup the system accordingly.
And to do things cleanly, maybe a SCR or MOSFET as the switch to handle the current surge without eroding switch contacts.
Isn't it better to use only air in the magnetic loop so you don't have any limit on the field strength?
@@paulcohen1555 No! So things like iron have relative a permeability in the 1000 to 100000s, meaning the B is that many times stronger for a given H field that it would be in air or free space with a relative a permeability of one. As we drive a core in to saturation, its relative permeability drops but will always be more than air. So go for a nice iron core, a bit thicker than your object to be magnetized so that the B field get scrunched together and gets bit stronger in the object to be magnetized.
@@qinaan
Please give the calculations that you used.
Have you considered attempting to create a monopole magnet?
Very cool. When recharging a magnet, I use a compass to determine the magnet's polarity. It'd be cool to demonstrate this for the community so folks can work on magnets that are not color coded.
That a great idea - a compass is such an easily available ideal for determining magnet polarity.
Glad you though the video was coll and thanks for posting the compass idea!
Your tapping on the magnet reminds me of a grade-school experiment to make a (very) weak magnet: hold an iron rod so that one end points north and the other south and then bang on one end with a hammer for a while. This uses Earth's magnetic field to (feebly) align the magnetic domains (or is it shifting the domain boundaries?).
Don't know if your video plans include a discussion of how magnetic shunts are used to current limit transformers (I think there were clues in your magnetic chain video), but I'm sure you could do it justice.
It seems for things like iron and steel its shifting the domain boundaries, but its really outside my area of expertise so I could be corrected by someone with more specialized knowledge. I have read that for things like computer disks and tapes the magnetic coating particles are each one domain, so presumably their direction has to shift rather than boundary moving. Maybe that's a way to make a really hard magnetic material?
Your tapping the iron rod experiment is exactly the same thing - the jolt presumably supplies a bit of energy to allow domain some walls to move which is what I was trying to do by tapping. Interestingly all I remember from school is stroking a nail with a bar magnet - maybe we didnt have any nice big steel bard to play with :)
Current limiting magnetic shunts: I have been thinking about that but it will have to wait till summer: I have an old 120V 100A arc welder that should be much easier to take apart to show the shunt than the 240V 200A one. Its in a shed in the yard behind feet of snow right now. Yea - there were clues in the chain video - its always a struggle limit things to keep the videos to a viewable length!
blacksmiths were the first to discover iron's magnetization via heat and pressure.
Aha! Now that's totally METAL!
:)
You sir should consider a career as a university professor. You have a way with words and a really soothing voice. Thank you for the video.
Thank you so much! I really appreciate that. I actually did teach at university for a while after finishing grad studies but ended up in the hi-tech industry for most of my career. I did enjoy the teaching part but truthfully would have gotten tired of it after teaching the same courses again and again. I still occasionally do stuff with a local university - usually judging their 4th year thesis projects or sponsoring/advising a particular project.
For what its worth, many of my videos (including this one) are modified from material or labs in 2nd, 3rd, or 4th year Electrical Engineering of Physics courses or labs that I have either taken or taught or both. But what I try and do here is minimize or eliminate the science and math background that is usually needed to keep things accessible to a general audience, but still present things in a way that is sill meaningful and properly represents the (often more complicated) underlying theory.
Thank you. I learned a surprisingly
large amount from this video!
Glad you liked it! I found magnetics amazingly interesting in university - had a great physics prof for the first EM course and also took his grad course on magnetic which was his specialty. His interest in the subject was infectious!
Nice video, very well explained.
Just one minor correction - at 14:08 where you show the B-H graph, I think you have the B & H reversed because the flattening of the curve is supposed to be for the flux density B which is the saturation point.
So H should be on the horizontal and B vertical axis.
Thanks! I just looked - the problem is sloppy labeling of the graph on my part. I drew the vertical scale on the left side and horizontal scale on the bottom of the graph. The B on the left is meant to apply to the vertical scale and poor positioning on my part placed it near the horizontal axis. Same for the H. Sorry about the confusion!
@@ElectromagneticVideos I wouldn't worry too much, I've made bigger blunders myself.
Take care.
@@markg1051 Thanks! Yes - in the grand scheme of thing its not big deal - hopefully most viewers understood what I meant.
I haven't had to deal with such weak ferrites, but AlNiCo compositions a low enough coercivity that they're easily demagnetized. Always have to keep them shunted and away from NdFeB magnets. I once had to do a bunch of testing with mortar fuze components that used AlNiCo cores, and I had to make a jig to remagnetize them. I guess that's the sort of inconvenience that happens when you try to reuse something that was meant to be used once before exploding.
So I'm really curious having never had anything to do with explosives. What do you use the magnets for - some sort of fuse or trigger? I would guess the shock of an explosion would also tend to demagnetize them ...
@@ElectromagneticVideos A lot of munitions fuzes have to do elaborate things where timing and sensing is required. Where some of those things used to be implemented mechanically with clockwork, it's all done electronically now. The problem then is getting electrical energy to power the microcontroller(s) in a way that can have a long shelf life (i.e. no active electrochemical cells). There are setback and spin-activated dry-charged cells, pyrotechnic generators, and other stuff, but a lot just use a once-through linear electric generator activated by setback. A tiny magnet gets snapped through a coil by its own inertia, which generates a single pulse which can be stored and used to power everything during flight. That poor generator only does its thing once before it (and the rest of the circuitry) gets destroyed by the main charge.
@@PSUQDPICHQIEIWC Thats amazing. - and clever! Almost infinite shelf life and probably just e enough power to get things done.
"That poor generator only does its thing once before it ... gets destroyed" I guess that so true for so many of our sophisticated weapons these days. And for many other things, microelectronics has become so cheap they are essentially expendable - RFID tags immediately come to mind.
Making magnets at the forge make so much more sense now that you mentioned the lava. 🔥
Have you actually made magnets that way - cooling the metal down while in a field? I have never actually done that - would be neat to hear how well it works in practice!
@@ElectromagneticVideos happens when you forge something facing due north or south till it cools and you hammer lightly up and down the bar to a plannishing heat. Super annoying when you dont want stuff magnetized.
@@williammorris1763 Oh - of course! How interesting. How strong is the field - can you pick up a bunch of finishing nails with the accidentally magnetized item?
Most normal iron and steel makes poor magnets - have you tried banging the item with a hammer when cool? That might demagnetize it...
@@ElectromagneticVideos enough to be annoying. Not sure about hitting it, i just use a demagnetizer. They sell mag/demag tools on amazon. Wiha? Like $20~.
Great and educational video, but i have a question: does it matter for how long the external magnetic field is applied to a weak magnet? If i charge a 2000uF capacitor bank to 400v and put like 5000A through my coil, will i end up with an extremely strong magnet?
Thanks you! The process of magnetization should happen very quickly - certainly the type of speeds we change the magnetic field in transformers for example. So if you setup a capacitor bank as you described and make sure there is enough charge to keep the peak current going for say 1/100th or a second it should work. The really nice thing about your idea is you can get away with much smaller wires that would be needed for a longer period of high current. It would be a great experiment to try and see if if it works (be careful with 400V!) . One thing to point out though - you will always be limited by the saturation and remanence characteristics of the material you are magnetizing so there will be a current value above which you get no greater permanent magnetic field.
@@ElectromagneticVideos Im very grateful for your reply, Thanks.
@@rekinek1111 Your most welcome! I really enjoy questions like that - its so interesting to think about something clever like that. If you try it, I would be fascinated to hear the results.
What happens if you heat magnet to curie point, apply the field, then rapidly cool below the curie temp before turning off the field?
It will be magnetized. It happens in nature: en.wikipedia.org/wiki/Archaeomagnetic_dating
@@ElectromagneticVideos i love your channel! Subscribed!
What is the most effective way to magnetize magnets in industry? Do they just put it briefly in a high field or do they do anything else special?
@@weirdsciencetv4999 Well thank you! Welcome aboard :)
You know, I don't know what the latest technology is for that and its a really interesting question - particularly for Neodymium these days. I did a quick google on Neodymium and one manufacturer does say exactly that - put it briefly in a high field. But you also wonder if there is any secret sauce that one or the other manufacturer may have developed and are keeping it a trade secret - a particular charging current profile maybe that works best? Some other trick? It would be fascinating to see how its done in a real factory.
Can you make videos about electromagnets ?
Thanks
Here it is! th-cam.com/video/LxY9M9Dznlc/w-d-xo.html
Can you detail how the coil is working?
i need a magnetizer, and I have some coils (transformers & old motors). None look like yours, and you used it in a way I never considered.
If you want a coil like that, its a standard 120V to 24V (I think) transformer. Some like this one are poorly constructed so the E and I shaped sections are joined with a shallow weld that a grinder can take care of. Better ones, the E and I sections alternate between top and bottom and are glued together - almost impossible to take apart. This coils was from a old APC UPS rated at 1000 to 1500W if I recall. Look in a recycling bin for somthing like that to get one for free :)
@ElectromagneticVideos no, I don't want another. I want to know how to use another.
i have no ultimate product in mind, I just want to understand it a bit better. I guess my goal can be to make a rudimentary compass needle.
Maybe I should power one, then wave a compass around it to see where the field is... I can use a normal compass like your mag-wand, right?
@@Iowa599 Yes - that mag wand is just a two axis compass!
To magentize a plain old needle for a compass, the easiest way is to just stroke it with a strong permanent magnet. Or use one of these: th-cam.com/video/AZsYHLHlIso/w-d-xo.html
@@Iowa599 Sorry - misunderstood. Yes - a compass is a great field detector. Be careful not to get it so close the magent pulls the pointer off its axis though.
Great video again! Regarding this I have a question about motors in my Nagra tape recorders. In these motors the rotor is a coil of wire with no laminations with inside there sits a permanent magnet which is completly enclose by the coil. To replace the ball bearing inside the complete coil and magnet has to be taken out of the housing. This then needs to by kept in a special cylinder (mu-metal?) so the permanent magnet doesn't loose its strenght. Can these Alnico magnets loose there magnetism so quick if it is kept outside of the motor housing? I found this rather strange. Its all in the manual and reads that if its not done like this the motor needs to be send back to the factory in Switserland to be re-magnetised. Sorry I can't show pictures of it here!
That is interesting! So when the rotor is removed, the magnetic circuit - that path that the field flows though now is mostly air rather than metal, which tends to encourage demagnetization (closer to the downward section of the BH hysteresis curve). If subjected to vibration or warmth (more energy to jiggle the domains around) down the curve you go and the field drops. Put it in a cylinder and you once again you complete the magnetic circuit and its much easier for the magnet to stay magnetized. Any reasonably thick iron or steel cylinder (pipe) should do as long as it is only marginally bigger in diameter than the diameter of the rotor. You need a close fit. Bang the rotor while its outside and the magnetism could be gone. So I think that's the manufacturers concern.
I'm a bit puzzled by the coil around the rotor. Is it powered to try and boost the field or keep the field at its peak? Or is it some sort of sense coil to provide some sort of feedback such as if the magnet slips out of synchronization with the stator's rotating field?
How do you use clamp meter on DC current?.
Some meters have magnetic field sensors that can be used to measure the DC field and hence DC current. Not as accurate close to zero as the transformer action based ones, but still very usable for most applications. They are remarkably inexpensive the days ($50 or so)
In oder to avoid high current, could time also have the same effectivness? (ex. in lieu of a few seconds at 60 amps, then 15 amps over an hour?)
An alternative method can be applying electrical current, while heating to luminescence?
It doesnt really accumulate over a length of time. You really need a high strength magnetic field so high current is a must (or many turns).
You right about heating - apply current while hot and above the Curie temperature and then cool down while maintaing current. Rocks thats were once hot like on the mid-oceanic rifts become magnetized by the earths field as a natural example of this.
Very good explanation....
Thanks!
Thanks for using Robertson screws in your high tech detector - they are much more accurate than dreaded slot and Phillips screws!
Ha - yes! Are you Canadian too? They are truly the easiest screws to use but sadly they are uncommon in most other countries. The History Guy did a nice video on them if you havnt seen it.
@@ElectromagneticVideos Indeed I am a fellow Canuck. I enjoyed your magnetic to electric circuit analogy. Many years ago, I taught a college course that included AC and DC circuit analysis as well as magnetic circuit analysis - I taught the material exactly as you did. Sadly, magnetic circuit analysis isn't on the radar in many programs.
@@carlosanvito Really? I haven't taught university courses for years - I'm amazed it is being left out. When I was an undergrad, it was in both the 2nd year physics introductory EM course and further elaborated on in the 3rd year EE machines course. We had some of the best profs for both courses - to the extent that I was not expecting to find the machines course very interesting and ended up thoroughly enjoying it.
@@ElectromagneticVideos I was in university a million years ago and at that time fundamental EM was taught to all engineering students in a first year course. That was a great primer for those of us in EE to better understand concepts around transformers and rotating machines that would follow. Communications and Maxwell's laws studies would be highly restrictive without EM basics. My observation is that basics are taking more of a back seat in favour of material which attracts more paying students.
@@carlosanvito I'll bet we were in university at about the same time (give or take a million years :)
I have come across that paying student shift - once hired someone from what looked like an excellent community college program . Turned out there was huge disconnect between what they said they taught and what the students learned - turned out the program was 99% percent students from one foreign country and grades were inflated to keep the students coming. I gather at the university level is huge pressure to make the courses "entertaining" at the expense of the fundamentals.
Great video! Looking forward to the demagnetizing video!
I have already shot it - still need to edit it. I have two vintage de-magnetizers I demo - one a tape bulk eraser and a TV repair loop CRT de-magnetizer - lots of nice colors when that near a the CRT TV in my workshop!
Maybe you could use the primaries from two microwave transformers. They could be offset to each side as you did here. Properly phased you do the entire magnet at once.
Yes - exactly! I was just making use of what I had on hand - by no means an optimal setup!
Fascinating and thanks for this explanation!
Thanks David!
pretty legit and thorough. good work.
Thanks!!!!
70 amps seems very high for a battery charger! Would this current not turn the water to hydrogen and oxygen. What about an arc welder with just a few coils of very thick copper to magnetise.
The charger's high current output is for boosting to start a car with partially charged or dying battery. Its an old one - no fancy electronics. When charging a typical 12V battery it typically puts out about 40A - a bit much but great when you are in a rush. And you right - that amount of current (or less) after a full charged will create hydrogen and oxygen in a lead acid battery.
An old style (DC) arc welder would work well too - its natural current limiting ability could be very useful for that sort of thing. Great thing about the old style arc welders is that they are are often available quite cheap in the used market. I got an old 230A vintage AC welder for about $100 a few years ago. The new electronic switch power supply arc welders would certainly have the current generating ability - but I'm not sure how well they would react to being attached to a coil - I wonder of they would determine something is wrong if they dont detect an arc and shut down.
Not the wire. Not the magnet. Does the electromagnet need to have a steel core or could it be made out of aluminum or copper for magnetize a magnet?
An electromagnet does not need to have a core at all - all you need is a loop (or loops) of wire with current flowing though it and and you have an electromagnet.
You could just loop some wire around a piece material you are trying to magnetize, pass a large current though it, and it would work. But you would need a lot of current.
If you have a Ferromagnetic material like iron or steel as the core of an electromagnet , it will increase the B field strength considerably beyond the the field without the core. Also, regardless whether the coil is around the magnet to be, or another core, if you can have a complete magnetic circuit out of steel or similar for the B field to flow though, you will get a higher B field up to the saturation limit of the steel and can magnetize with a lower current.
For really high strength superconducting magnets, you often don't use a core since the currents are so high the field beyond the saturation limit of iron or steel and the core would have little effect.
Hope that helps!
Something I saw years ago....a guy in a shop I worked at had salvaged a coil out of some ballast...even with the iron core removed, it weighed a couple pounds. He wired a momentary contact switch in series with it, and drive it off 120 volts ac. Done just exactly right, you could magnetize and demagnetize with it. It might take several attempts to magnetize something...you had to hit the switch quick, but you could do it. Never tried this myself, but it worked...
Doing it with AC is wild. I guess if you turned it off after the current has reached a peak (ie max H field) and before it reverses your would end up with a nice strong field. So the second half of every half AC current cycle. So maybe 50% of the time you win, 50% of the time you loose. And furthermore, pressing it for a really short duration can result in high inrush current to that is still there when the switch is turned off.
How clever!
nice tutoring, followed by excellent application of theory.. you got an instant sub here sir.
Thank you so much Emre! Really appreciate your comments. I hope to be uploading more stuff middle of next month. Unfortunately have been too busy with work to do any videos in the last month :(
Explained so clear, so simple and so complete and so interesting ... I'm gonna remagnetize the magnet of my woofer. I think it will work. Thank you for the info, well done ! Greetings from Belgium. PS : Is it possible to DEmagnetize a magnet or something magnetic wich may not be magnetic / might not become magnetic , and if Yes, How ?
I'm glad you found the video simple and clear. A few thoughts: I think the hardest thing will be making a suitably shaped magnet core to fit nicely against the woofer core. Also, try and make the iron in the core you build have a greater cross sectional area that the woofer core, so the magnetic field is squeezed a bit to increase the flux density at the woofer core. And wind lots of turns of wire around the core you make - all along it. And be sure to get the polarity right to so you are adding to whatever remaining magnetism there is in the woofer.
There are videos from people who have made magnetizes, so look at them too if you have a chance. I'll bet someone has done woofers.
Demagnetizing: Have I got the video for you! th-cam.com/video/mGK8oYdEqyE/w-d-xo.html
Greetings from Canada!
Thanks for walking us through the basics.
I recreated the magnetism of those horseshoe magnets that are in old phones to make the ringtone, once.
I just wound on coarse wire and connected to some series connected car batteries, nothing you should do.
- But it worked!
Its really neat how easy it is to make an electromagnet. Course wire works fine - and for any wore, the more turns the better. One caution for anyone reading this - car batteries can deliver so much current the can be a bit dangerous for this sort of thing, but a few plain old household D batteries are usually enough!
@@ElectromagneticVideos I believe while magnet is hot (and cooling) or if the metal is repeatedly and firmly tapped while still in the wire coils it can pick up some permanent magnetism like you shown.
@@harrymu148 Agree completely! It would be interesting to know if it starts out hot enought whether tapping would even make a difference.
THANKS FOR ANOTHER GREAT VIDEO!!!
Between timestamps about 9:10 to 9:15 while you were talking about the 'magnet resistor', the word "RELUCTOR" popped into my head!
Also, have you heard that they were (for a while) actually selling school magnets with "N" and "S" REVERSED!! It had something to do with the fact that teach that a magnetic compass will always 'point north' so that the compass will demonstrate that earth north will actually be demonstrated....I think they stopped this nonsense.
I got a few of those pole indicators, like you shoe at about 11:10 One was actually hand labeled "Green = North" (none of the others)?? I ignored this.
One more thing: When you were REmagniting a material why doesn't the alternating, AC, magnetic field just push and pull the domains, leaving no net effect.
THANKS AGAIN....still catching up on your fantastic videos! Please keep them coming.
--dALE
Thanks! Glad you enjoyed it!
I just googled "reluctor" - seems to be a sensor type commonly used in cars for crankshaft position based on magnetic reluctance - how interesting!
I had never heard of magnets being mislabeled the wrong way for "educational" reasons, but doesn't surprise me! Still strange!
Remagentizing - did I accidentally imply I was using AC? If so, it should have been DC. I have heard of people using AC which works if you turn off the current close to the peak of the cycle. You then have a 50 % change the magnet is magnetized one way or the other. Apparently do it a few times testing the magnet in between and it eventually works.
More videos coming - if you havnt seen the "Measure the speed of light" video, take a look. I'm working on the DIY followup for it.
@@ElectromagneticVideos Yes, I have seen the "Measure the speed of light". Remember, we had a brief discussion on modulating HeNe's?? BTW: What's your first name...may help getting acquainted for TH-cam.
@@ElectromagneticVideosI just re-watched the video. I assumed AC since it was a transformer core. I guess you did, indeed, indicate the current was DC when you applied power with a battery charger. AND when you used the B-Field checker....sorry
--dalE
@@dalenassar9152 No worries! Its funny - I am always amazed at how I misspeak when doing videos so I would not have been surprised if I had got it wrong! I think in normal conversation we make more errors than we realize, but not being recorded they are so fleeting they don't get noticed. You wouldn't believe the amount of editing or re-shooting video I do to correct what I say!
@@dalenassar9152 Strangely I just saw your "Yes, I have seen the "Measure the speed of light". Remember, we had a brief discussion on modulating HeNe's?? BTW: What's your first name...may help getting acquainted for TH-cam." comment - it was quarantined for review!?!?!? TH-cam seems to sometimes get confused about what good and bad. Yes - I remember we had that discussion - sometimes when lot of comments come in its hard to remember who I had what discussion with and there does not seem to be and easy way to see what discussions I have had with anyone in a different video. BTW - I tried once to change my comment name to "Pete @ ElectromagneticVideos" but was unsuccessful. Will have to try again!
Very nice video. I use a very strong neodymium magnet rated at 600 hundred pounds of pull, I don't know how much gauss it produces, I don't have a gauss meter to check it. I do use the neodymium to recharge my alnico magnets and does make them strong again, I'm sure it's not full saturation, but they are strong again.
Thanks! That's really neat to have used one permanent magnet to charge another - makes sense with a strong neodymium magnet. Do you have anything like shaped piece of iron to guide the flux from one magnet to the other and compress the flux into a smaller area to raise the density closer to the saturation point? Thats really what would would have liked to have for the demo I did.
By the way - great vintage videos you posted of electrical demos! Just subscribed so I can watch the later!
@ElectromagneticVideos
Thank you for subscribing, I will be posting more later. To answer your question, I just touch the neodymium magnet directly on the Alnico magnet, North pole to South of the neodymium, and then turn them around and repeat the process.
I subscribed to you as well.👍
@@bobthescienceguy2144 Looking forward to more posts!
Neat that doing something as simple as you are doing charges the Alnico!
@@bobthescienceguy2144 Thanks!
Very nice video, Sir, however i have a question regarding this video. In this video you talk about high current and moderately low voltages. From a welding machine i guess 48 Volts. On another video thats called 'MAGNETS how its Made' from Discovery UK they say that in the first step (high current/low voltage) they prepare the magnets for establishing the polarity, then in the second step they use High Voltage, low Current to really magnetise a magnet, (in that movie 30 Amps x 300+ Volts). So i am a bit confused now. Can you clearify this. Thanks.
Thanks! I tried looking for the video you mention but couldn't find it it so I will make some assumptions about what they are doing.
You mention that they initially using high current/low voltage to prepare the magnets. Are the magnets hot or even molten at this stage? It might be to try and orient the domains or crystals as the material cools in a way that is optimum for the a magnet with with fields in the desired direction. I'm guessing only a small number of loops in the current carrying wire.
2nd step: HV, low current 30A 300V. For the final magnetizing step you need to force a field somewhat above the saturation level of the material. The H field that does this depends on the Amp-Turns of the coil, so you need a minimum number of amp turns. You can have a few turns with high current (eg 10 turns at 1000A = 10000 Amp turns) or many turns at lower current (eg 333 turns at 30A = about 1000 Amp turns) . How you get the required number of amp turns doesn't matter and would be chosen based on what is easiest to wind given the geometry of the magnet and the easy availability of suitable power supplies.
The voltage that is needed is determined by the total resistance of the wire. More turns = longer, usually thinner wire so more voltage is needed for a given current, which is partially offset by the need for less current.
Bottom line - they used many turns to need less current and used high voltage to push that current through a thin, long wire. I used a few turns of thick wire. I probably didnt mention the alternate option of many turns and lower current - often the videos have to be kept somewhat simplified to avoid confusing or complicating the concepts being presented.
Hope thats helpful!
@@ElectromagneticVideos Thank you very much for this great and fast reply, i really appreciate it.
I am trying to magnetise U-shaped O1 tool steel that is hardened and tempered. For the magnetisation i use a welding machine as power supply (48v AC), then a bridge rectifier to make DC. That DC is connected to the primairy (thick) winding of a microwave transformer, so +/- 3 Ohm. When i magnetise this U shaped tool steel i can not get higher then around 30 Gauss. So i thought i go check online and found this video.
th-cam.com/video/qed4ynPYVIA/w-d-xo.html
So that leaves me with 2 more questions if you don't mind. 1. Is there a way to find the magnetic saturation level of this hardened and tempered O1 tool steel? and 2. Would the tempering proces (in my case 2 times 2 hours of +/-200 degrees Celcius heating, then slowly cooling) have an effect on the magnetisation level?
Anyway, thanks for the effort and happy new year.
@@germona Interestingly I geographically blocked from that video!
Your questions: 1) The saturation level for most steels is between 1T and 2T. If you estimated the current needed for 2T you are almost guaranteed to be fine. If you can measure the B field, and do a few readings for different currents, it should be obvious when you have reached a current level where the field does not get much stronger. There is a nice graph here: en.wikipedia.org/wiki/Saturation_(magnetic) 2) I'm not sure how the tempering process would affect the magnetization level that can be achieved - I would think it will affect the magnetic hardness hardness (how easy/hard it is to loose the field after magnetization) because the crystals and stresses in the material will alter how easy it is for the magnetic domains to change. I'm not sure if tempering - or cooling the steel quickly will make it better or worse. I'm sure somewhere on the internet there is some practical info on that. (let me know if you find out!)
In general "normal" steel as found in tools does not make great magnets as it is magnetically soft so it will generally make magnets that easily loose their strength which is why other materials are usually used to make magnets. Depending on what you are trying to achieve, you might find you get better results is you use a alnico or neodymium magnet of about or bit more than the cross-sectional area of your piece of steal and use the your steel to guide the field to where you need it.
If you are just experimenting to see how to make magnet, keep experimenting. I did have a large steel horseshoe magnet as a kit - it worked - but was never very strong and quite weak compared to what we are used to today.
@@ElectromagneticVideos Thank you again. I am trying to make a horse-shoe guitar pickup, like in the rickenbacher frying pan A24 lap steel guitar, that was invented by George Beauchamp in 1932. It is not very much magnetic but a little more then i can get now. If you search in your browser for images on 'horseshoe pickup lap steel' you will see a lot of examples. I have a rickenbacher lapsteel from 1946, and that magnetisme is still there, and that is the amount of magnetisme that i am trying to archieve. I will keep on trying. Thank you for the help. Jean Belgium.
@@germona You know, someone else asked about that a while ago. Did a bit of googling and I now see what you are dealing with. At least one video I looked ta did seem to indicate after recharging the magnet the most yo could hope for is a year or so of use before needing to repeat the process.
Here are some thoughts: I did some research on annealing steel and magnetism. Annealing can increase steel's magnetic permeability (higher field for a given current) but decrease magnetic hardness (easier for the magnet to loose its strength). So it would seem steels that have not been annealed generally make better permanent magnets. I am wondering if over many years the steel gradually undergoes similar changes - reduction in internal stresses - as when it is annealed and so that what was a good steel for a permanent magnet when the guitar was made is no longer that good for a magnet.
Some thoughts - you could try heating the steel to almost red hot and then rapidly cooling it to harden it which might help. However I would be hesitant to do that on an antique item like you have and presumably like me. you have little experience doing that sort of thing. I did see one fellow who re-magnetized it by swiping a string magnet along it. You could try that and maybe swipe it with a magnet before each use. Even better, is there some place underneath where you could glue one or more strong magnets to the old horseshoe magnet? That would keep it permanently charged and might be the simplest solution.
Let me know if you find out what works best. Good luck - what an interestg project!
I am the first time to see your videos. It is very well executed and explained clearly. I wonder what your current supply look like. Thanks again for your wonderful video.
Thank you so much! I am gradually learning how to do these videos and I think they have gradually gotten better as I do more of them. It has been great fun because they have given me an excuse to do many ofthee things that I haven't done since I was a student!
@@ElectromagneticVideos do you mind show me your 100A power supply? 😀
@@manla8397 I don't have a photo of it right now, but it is an old analog automotive 12V battery charger that can put out 100A or more to also help start the car. You really need the old analog style ones for this because the new switching power supply ones will do all sorts of things and detect its not a battery and turn off. You can also use a variac to control the output of the old style charger.
You could also use an old style arc welder controlled by a variac. If its an AC welder you can get a 200A bridge rectifier to make DC.
Definitely more intrigued to learn about electro magnetism and more of physics as a whole I never payed attention in class unfortunately but science and math where always interesting topics. Nice video thanks for the simple explanations
Thanks! That's exactly what I am trying to do with this channel - make those interesting things understandable without the significant science and math background normally needed. More videos in the works!
Thank you. I left a like and ill subscribe. This is amazing to learn.
Thanks you so much! I really appreciate it!
As a geolist I apreciated that you talk about paleo magnetism.
When I was a kid that always fascinated me. I remember reading about it in some National Geographic article (probably from the '50s or 60s - my dad had a huge collection of NGs) I think about showing the spreading of the sea floor around mid-oceanic ridges.
@@ElectromagneticVideos I know about some discovery about locations where homo sapiens live. They found magnetic anomalies where the fireplace was
@@gfr2023 You know, now that you mention that, I do remember reading about that too. I think they were able to get the date of the fire pretty accurately from the direction of the captured magnetic field and knowing where the north pole was at different times - and that maybe from the mid-ocean rift data.
Yeah!! You have a great channell that I subscribe. I have in store some magnetizers coming from '60 magazines, very cool stuff for the home shop
@@gfr2023 Thanks! This morning I subscribed to your channel! You deserve way more subscribers!
Perfect video that I was searching for long time,
but I have a question :- can you make another video to explain the side by side (magnetic N = bottom of metal, magnetic S = top of metal) + thks ❤
Thanks! I quite understand what you are referring to. Could point to the point in time of the video and try and describe the question a bit differently?
Well explained
Thanks!
Hello, are you thinking of doing a course on these topics (Electromagnetism and Electrical Machines?), I mean, because electromagnetic circuits and Gauss Equations are not exactly topics of general culture jajajja, take care and good luck with your channel.
Sort of. What I am trying to do is bridge the gap between the mathematical treatment of electromagnetics etc as done in typical university level courses and the handwaving descriptions used elsewhere. I have been occasionally showing things like Faraday's or Ampere's and saying things like the first part of equation is the curl - think of it saying if there is a circulating field like a whirlpool ... . So I hope to give those without a rigorous EM background a sense of how things work, and those with the math, a sense of how it applies to practical things. I don't plan on give an online course on EM since thats been done a million times before :) At some point I might do a more organized series of videos to create a pseudo course though.
@@ElectromagneticVideos I understand, thanks for your answer.
@@angelandrade1780 Your welcome! If you have anything you would particularly like me to cover, please let me know!
We used to magnetize screwdrivers with a car battery and a piece of stranded copperwire wrapped around the screwdriver. the more turns the better ,, then we would short the 12 volt batter leds across positive and negative till the wires were smoking then after lettting it cool off we had amagnetized screwdriver which was way stronger than the pocket ones . Automotive hacks fro picking up screws ect out of intakes or disributors back in those days .You have made a few comments in regards to heating up the metals to line up the direction of the north and south poles in the structure of the atoms inside the iron. This is how the majority of ferrite and neomydium magnets are made in the industry . However certain metarials added will increase the feild strength as well as be subject to the breakdown polarization of the atomic structure inside the magnet it self. .
most applications as far as the hobbiests will ever use themm for do not go beyond 100 degrees f.. however certain kinds made for the Areospace and space industry have higher breakdown temps due to thier conditions in outerspace. Have fun in creating your own magnets. I tried a dc welder the other day to try to magnetise an iron nail.. i couldnt hold the wire feed long enough on the wires to create a long enough field . tommorow i will try heating the nail first and using more wrapps around the nail and then quench it in cold water to see if it will retain the magnetic field. ty for your basic presentation of the magnetic theory. the coils setup that you made i had completly forgotten about .. I have always been into magnetic induction and fields ect since i was a teenager. im 61 now and retired and have nothing but free time to enjoy this one of many favorite hobbies of mine.
I have heard of variation of what you described. I guess the trick is to do it just long enough but not so long that the wire melt from all the current available from the battery?
@@ElectromagneticVideos yeah that s the idea,, fine wired cabling works better than solid core ,as in house wiring though it will work.. just need alot more turns ,and fry your battery too.. better to use stranded wire as it carries more current ,, i have melted down wires before and they do have a tendacy to catch on fire ,,so beware .
@@randallmarsh446 " i have melted down wires before and they do have a tendacy to catch on fire ,,so beware" Yes! Might not be a bad idea to make a "fuse" with a length of slightly thinner wire to protect the bigger wire and battery...
Never knew that tapping the magnet 🧲 helped the alignment process! 😊
Thanks!
Just so its clear, if you have a really strong field to charge the magnet with, no need to tap, but if the field doesn't create saturation in the magnet being charged, tapping can provide a bit of energy to help the domain boundaries move. Also, not sure of how well it was shown in the video, but magnets are often brittle and if you tap them too hard bits can break off.
Do you ever blow anything up like ElectroBoom?
Occasionally, but this is not really a "blow it up" channel! Look here th-cam.com/video/k0g2LinZWyA/w-d-xo.html
Very nicely put but I still in my own right think that the domains are really nothing more than the attom of certain metals having more free electrons which creates a higher covalant bonding and the north and south characteristics are because of the manipulation of electrons making up the negative magnetic pole realative to the stationary protons the positive magnetic pole.
Here's the thing: if you have theory for magnetics or anything else that you believe is better than the existing ones, you have to demonstrate it by showing: a) that it correctly predicts what the current theory predicts correctly b) that it correctly predicts some things that current theory gets wrong (ie current theory has a flaw that can be shown by an experiment yet your new theory does correctly predict the result. )
Part a) confirms that it is at least as good as existing theory
Part b) shows that it adds something of value in addition to existing theory.
If you have both, you may have a winner! With Classical Electromagnetics, achieving the above is not easy - the existing theory correctly predicts so many things so well, and its main missing points are filled in quite nicely with Relativity and Quantum Mechanics.
So the challenge to you is, make a youtube video explaining your theory and also demonstrates with an experiment how it fixes some error in what the existing theory predicts.
@ElectromagneticVideos Yes, my comment on your demagnitizing video acknowledges that. But now I have to unsubscribe because you are taking my comments as an insult rather than what they were intended for. I was merely trying to have an open-minded conversation to stimulate and motivate critical thinking. Have a nice life.
What was the voltage used on the coil? You said battery charger so 6,12,24vdc?
It was a 12V battery charger with a high/low setting so probably between 15 to 20V. Since the resistance of the coil is really low it really didnt need much of a voltage to drive that much current.
Is there anything you can do to a magnet so that it will keep its magnetism longer?
Other than heating it up when you magnetize it I mean.
If you mean whne you are magnetizing it, no - assuming you are are already subjecting it to a good strong field. Howevern, once magnetized, there are a few things you can do to keep it nicly magnetized: 1) Put a steel bar or similar between the poles to make it "easier" for the B field to stay high on the BH curve 2) Dont subject the magnet to vibrations or shock 3) Keep it cool 4) Dont force it near an opposing magnetic field.
What I did leave out is all of this depends on the material the magnet is made out if some - some are more or less vulnerable to any of the items listed above.
I want a lot of these vedios
Here's a playlist of a bunch I did: th-cam.com/play/PLHUfJmsprIcRgeatuwmJkMYf-hEFvwR5E.html
@@ElectromagneticVideos many thank
Good video man, thanks.
Thank you so much! I really appreciate that!
I must be asking something already addressed. Sorry. But, for the transformer, did you remove both the primary and secondary and not modify them at all? Last question, in this video you connect the input terminals of the primary to your 240 volts AC wall outlet and you did not connect the secondary terminals to anything. Correct?
*...primary and secondary windings...
actually one more question. will there be anything else I need to know if my system uses 120 volts AC
@@ga28282 The transformer is an auto-transformer - it has a winding with a tap on it. For these purposes it doesn't matter. What does matter is the number of turns on the coil and the thickness of the wire.
To magnetize something, we dont use AC - we use DC. I am using a an old style car battery charger that produces about 20V DC or so at up to 100A depending on the resistance of what it is connected to. So the thicker the transformer coil, the less resistance. Measure the resistance with a voltmeter and you can determine the DC current that will flow for a given voltage which will be much more than the AC current the transformer normally carries. In my case the AC transformer would have been rated at 120V at 8A for a few minutes. As you saw I could push 70A DC though it (but only briefly since I dont want the winding to burn up with all that current).
We want to maximize the magnetic field which is determined by Amp-turns - the current times the number of turns. For a surplus transformer with a 120V or 240V primary, usually the primary is the coil to use. Try it at a DC voltage of 5 to 10% of the rated AC voltage. If the DC current is more than the rated AC current, OK to do it for a few seconds - but be careful not to overheat the coil.
Hope that makes sense!
Oh - you can put the secondary in series for a bit more field - assuming you can figure out its correct connection to increase rather than decrease the field. If is a 10:1 transformer you would get 10% more amp turns which may not be worth the effort!
@@ElectromagneticVideos I will take a look. Thank you. I have a 0-30 volts DC power supply that does up to 10 amps. We'll see what happens. Thanks I learned plenty from you
I have a magnetic implant, a neodymium magnet 2mm by 1mm, its inside my finger but over the years has lost its power, any ideas of how I can re-magnetise it without burning or electrocuting myself???
Obviously, I cant provide any medical advice. To re-magnetize a magnet, you need to subject it to an intense magnetic field, which will also STRONGLY pull magnet. I would be really concerned about about that causing all sorts of damage, possibly ripping the magnet right out of your finger, and maybe in the worst direction possible. So I sure wouldn't risk anything like that. Sorry ... not the response you probably were looking for.
What is the time duration of magnetic field required to magnetize typical steel?
That a good question and one which I don't know the answer! But its not very long - a fraction of second depending on the material. Its essentially the same mechanism to magnetize an electromagnet into saturation and transformers can go into saturation well beyond standard AC frequencies of 50 or 60Hz. I know people use charged capacitors to very briefly push an enormous amount of current though a coil to magnetize magnets and that would also probably in the fractions of a second.
If anyone has any experience charging magnets using a capacitor, would be great to hear how long!
@@ElectromagneticVideos
That's what I plan to do.
A big HV capacitor.
Few thick copper wire coil.
A fast high Current high Voltage switch (Thyristor)
That's all, very SIMPLE.
@@paulcohen1555 Perfect! If you do it I hope you make a video - I would be interested to see how it turns out. One thought - you don't need giant thick wire. Something like household wiring wire can do hundreds or thousands of amps as long as it is only a fraction of second. You may have to experiment with how many turns is optimal. If you are using HV more turns will be better. If you have scope clip the probes on the ground end of the wire you are using with only a few inches of wire between the two scope clips. The wire will be like a really low Ohm resistor and you can watch the current decay but also see its peak value.
@@ElectromagneticVideos
Sure.
And of course I will do some estimations and calculations of the circuit.
@@paulcohen1555 Good luck!
You can also magnetize by a lightning strike if you manage to catch one.
It does burn your fingers though :) Seriously - yes! That's how lodestone (aka magnetite) apparently gets magnetized.
7:57
Why don't you just place the coil around the magnet? Why do we need a steel core?
You could, but to get the same level of B field (ie to saturation) with a similar current, you would still need and iron path connecting the two ends of the magnet together to make it easier for flux to flow.
If I am understanding you properly, a large, steel, C clamp whose frame was wrapped with an electrified coil of doorbell wire would be perfect for magnetizing a bolt or a nail and making them permanent magnets.
I never thought of a C clamp for that but - YES - great idea! You would want the metal in the clamp to be thicker than the magnet (so at its saturation point there is more than enough flux to saturate the magnet-to-be) and also the have the magetic path though the clamp as short as possible (so smallest clamp). This would minimize the amp-turns needed.
The only issue with a bolt or nail is generally they are not ideal materials and tend to be vulnerable to easily loose their magnetisim with the slightest misuse.
@@ElectromagneticVideos Thank you. My thought is to take a rotary hammer SDS point bit (primarily made of carbon steel, normally used for smashing stone) that has lost it's point through over use, grind the point area flat, heat treat and temper it, then put the new flat flat end in a C clamp as described, magnetize that end and use it to hold nails as the rotary hammer hammers the back end in thereby driving nails with a rotary hammer. Just something to do while bored.
@@ElectromagneticVideos I have an old C clamp I made in shop class a few decades ago out of heavy steel with a steel frame about an inch and a half thick in all iirections. Should be perfect for the task.
@@kenibnanak5554 Your Welcome! Thats a neat idea - I would be vey interested to hear how well it works. The concern I would have is the violent hammering action on the bit by the rotary hammer + the open magnetic circuit on non-ideal magnetic material would rapidly demagnetize the bit. The tempering may help make the material magentically harder (I'm not 100% sure) and retain the magentism better.
If you find it does loose its magetism after some hammer action, one option may be to mount a magnet very near the bit close tot he chuck. Would be tricky to get it gear enough without touching - maybe a held with a thick piece fo steel with a bolt into the threaded hole where the side handles often screw.
Anyway - go for it! Should be interesting and potentially really useful.
So damascus steel is highly magnetic?
I dont know about it in particular, but most steels are. There are steels like silicon steel that are designed for specific magnetic and electrical properties.
Learned a lot. Thanks. Doesnt a type of welding-iron uses the principe with the curie-point ? And that don't seem to be "dangerous" for the magnet. (And a trivia: In swedish BH is the same as bra.... :) )
Your welcome! Not sure what you mean with the iron in terms of the curie point. If you elaborate it might help. I think your referring to what I would call a soldering iron which melts a tin+something (lead in the old days) to attach electrical wires or devices. The alloy is not normally a magnetic material so it no risk of magnetizing it.
Most soldering irons operate by a resistive element providing the heat and with little current flowing there is little magnetic field. Solding guns however use a transformer to create large current to heat the tip and there is a huge field as shown here th-cam.com/video/mGK8oYdEqyE/w-d-xo.htmlsi=heddjVD9ww3PlMmJ&t=537 . So that could demagnetize nearby magnets.
Trivia - I'll bet that is the source of endless amusement in introductory electricity and magnetics classes in university :)
Does the magnet need to be touching the magnet system for it to be connected
It doesn't need to be touching, but the larger the gap is, the lower the magnetic field from the electromagnet will be and so the effectiveness of the magnetizing process will be reduced.
As long as field is somewhat greater than saturation value of the permanent magnets material it should work fine, just this will be harder to achieve with a bigger gap.
@@ElectromagneticVideos Thanks, I appreciate it highly say for arguments sake you passed a permanent magnet through an electromagnetic field indefinitely in and out of the field would it then holds its charge forever in theory?
@@helpyousleep8173 I'm not sure what you mean by "passed a permanent magnet through an electromagnetic field indefinitely in and out of the field". Bottom line: if you have a good magnetically hard material for your magnet and expose it to a nice strong field (above its saturation level) to charge it, it will hold its magnetism well. However, do "bad" things to it like forcing the like poles of two magnets together, and maybe even banging them at the same time, and the magnetism will be reduced or lost.
@@ElectromagneticVideos I’m currently designing something, could you point me in the direction of any text books that go in to mass detail?
@@helpyousleep8173 If the want a general electromagentics text book, Electromagnetics by John D. Kraus is the one to get. It covers all the theory and includes applications. But you will need some math background, most importantly vector calculus. From your questions it sounds like you are more in need on something specifically dealing with magnets and some very hands on advice on making them. I dont know of any specific book that covers the the very practical aspects of making magnets more from a production and manufacturing process. So unfortunately the best advice I can give is google or go to a university library, or even better better, a university Electrical Engineering library or Physics Library and browse the appropriate section. You know, even searching TH-cam might bring up what you are looking for.
Why permanent magnetic fields are not source of electricity???
What happened if we use a negative terminal as earth and potential difference between high magnetic fields and equivalent negative impact by earthing??
Why don't you move the magnet down to magnetize the other half instead of reversing the polarity?
To make sure we are understanding each other you mean slide the magnet to the left so the right side of the magnet is now over center leg of the old transformer core, right? That probably would have worked but would have also applied a small reverse field over the shifted left side of the magnet which (depending on strength of that field) might have had small demagnetizing effect on the left side of the magnet.
The real issue is that the permanent magnet I used was to big. Ideally its ends would be the same distance apart as the two left legs of the old transformer core. And for that matter one really needs just a U shaped core for the electromagnet as opposed to the E shaped transformer core.
Thanks😊
Your welcome!
I did something to a magnet, destroyed it with a stronger magnet somehow, but don't know how too explain it.
Well I guess I do..
I was pushing a smaller magnet against a larger neodymium magnet, opposing, and the little one just gave out all of a sudden.
No more magnet.
Thats too bad - but not uncommon. When you push the same poles of two magnets together, the fields try and shift the domains in the other direction. Do it a little and you manage to move some of the domains such that the field is diminished. Do it with a really strong magnet and you can magnetize the smaller on in the opposite direction but its hard to get the field strong enough to do that. So in your case the big magnet managed to reverse the domains at least party in the smaller one reducing its field.
Basically a magnet is a trapped polar charge. And any magnet in any form is in fact a permanent scalar wave emitter.
If a single coil with sufficient length of wire will pas through permanent magnets and magnets are placed at a distance equal to 1/2 of wave length corresponding to frequency of the alternating current voltage will will be greatly amplified while ohmic resistance in wire will be reduced by 95%. The higher the frequency the shorter distance between magnets where they MUST be placed exact where 1/2 of wave length is (max amplitude)
This a different way to exploit permanent magnet effect and not only 200 years old methods … ie Faraday, Lentz
Manipulate magnetic field to create electricity or manipulate electric field to create magnetic field/flux
Remember, two separate electron flow running against each other create scalar waves, zero point energy or whatever name scientists use for this effect. And all this is possible because existence of aether … Galileo Galilei said: E pur si muove !
Magnetic field means instant action at distance … instant is obviously faster than speed of light, yet mainstream science deny it against all evidence !
8:48. Why bother with a steel core? Couldn't one simply wrap a coil on the magnet? Run a current through coil and maybe tap the magnet to jostle any remaining stuck domains into alignment with the applied field?
Then you went into magnetic circuits and the resistor analogy. The seperate C shaped iron core represent a low reluctance path which helps complete the magnetic circuit with a low reluctance path which allows (creates) a stronger magnetic field throughout the magnetic circuit than if there were more high reluctance paths in the magnetic circuit.
The second half of you comment is why - the low reluctance C minimizes the amount of current (or more accuratly amp-turns) needed to achive the required field in the material you are magnetizing.
You could certainly do it without the C exactly as you describe - just more turns of the coil and more current. In the end it just depends on what is easier.
@@ElectromagneticVideos I'm sorry I may have worded my inital comment a slightly differently than I intended it to be understud. The first half was a question I had, and the second half was me figuring out why use a core for magnetizing after you gave a simple magnetic circuit analogy analysis. 😁 A question asked and auto-answered.
@@kreynolds1123 No worries! Nothing like a self answering question :)
EXCELLENT EXPLANATION
Thank you! Really appreciate that!
Very Good Video! Thx!
Thanks! Glad you liked it!
Great Video!
Thanks!
error : the batyery equvalence makes sense only when the magnet moves relative to the coil.
Not quite sure what you mean. Reluctance circuits are a pretty standard way of approximately calculating magnetic fields in this sort of situation. Here is a link a that describes it in a bit more detail: eepower.com/technical-articles/magnetic-circuit-properties-understanding-reluctance/#
It is a superior magnet tester made with Robertson Screws, that every Canadian knows are superior for all applications.
Absolutely! Other countries don't know what they are missing!
one millimeter is a bit bigger than a thirty second of an inch (0.0315" vs 0.039")
Eighth of an inch is closer to 3mm
I stand corrected :( Sometimes when making a video ti many things going on and dont have time to think carefully about things like that.
8th of an inch is a millimetre in US?
I guess I goofed on that one :) 16th would have been better. I find its surprising how many times I say things like when thinking out loud while videoing. I suspect we do it all the time in normal conversation just there isnt the playback to make is so obvious!
@@ElectromagneticVideos Thanks for your reply. I understand of course, I just found it funny
@@hongkongkong7174 It is! And a bit shocking how many inaccuracies pop up when I edit the videos - you wouldn't believe how much I have to correct when editing. I guess that's why the pros use scripts!
@@ElectromagneticVideos happens with me too and I'm 27 only. I teach science and I deliver the lesson impromptu style i.e. I have no scripts as well.
just noticed you're not in US anyways 😂, it's close enough I guess 😉
Nice video, well done, thanks for sharing it with us :)
Thanks! Glad you liked it!
ok i have an old permanent magnet generator from the 1974 its 1800 watts it was my dads. it was handed down to me.. It sat in storage for years . when i got it and started it up it only did 800 watts i thought ok 800 watts i shut it down .. the next day i started it to show my friend it then made the 1800 watts???? i guess I'm picking your brain lol... my friend says the magnets had just rejuvenated... is that what happened?
That's really interesting! So assuming its AC, there are some interesting behaviors that are associated with AC motors and generators. If you have an inductive load attached to the generator (like a typical AC induction motor) the field created in the generator from the lagging current flowing to the load will tend to oppose the magnetic field in the field magnets and potentially try to demagentize it. A capacitive load (rare) will draw a leading current and tend to strengthen the field. Maybe there is a capacitor in the generator to encourage that, although I have never heard of that being done in a permanent magnet generator. Its typically done for induction generators.
Another possibility is a series field winding to strengthen the field when more current is drawn (simple voltage regulation) . Thats typical of electromagnet field windings but could be done in permanent magnet ones I suppose.
Of course with all of that said it could be something simpler: Are there brushes/slip rings? Could it be they got cleaned up after a bit of use? Or maybe some connection was poor and heated up and fixed itself?
Has your friend seen magnets get rejuvenated before in a generator? If so thats really interesting - I'm an EE but haven't done much with motors/generators since university. How did you test the wattage? What type of loads?
It wasn't all that permanent then.
Ha! Yes - I guess it wasn't :)
my magnets are running out?!?!?
Did I say that somewhere?
hell yes i like it
Well thats an enthusiastic response to the video! Thanks!
All I know is... last time I had to make a magnet from scratch I did it quite a bit differently.
So .... how did you do it?
@@ElectromagneticVideos stuck a really powerful magnet to the side of a metal bucket. Filled bucket with water.
Heat piece of metal in a forge to above it's curie point. Quickly quench the hot metal close to the magnet in the bucket... and Bob's your uncle.
@@sideswipe147 Never heard of it done that way - clever way quickly to drop the temperature while in the presence of a magnetic field!
@@ElectromagneticVideos yeah well once upon a time I had to figure out how to make a magnet without macnets. It evolved from there.
in reference to demanetizing an object, grandpa showed us that you could use a spark plug wire to zap what ever you wanted to demagnetize by allowing a spark plug off the engine to arc across the object a few times.. but wear gloves when you do this engine coils are extremly unforgiving1and use a pair of no elctrical holding devives such as a plastic tong from the kitchen an not a pair of plastic coated needle nose plyers..haha
Interesting that a spark plug type zap would do it since the current isn't generally that high. I wouldn't trust the plastic on pliers or gloves for that types of voltage - an yes - I have been zapped before :)
Why would you need to (re)magnetize a PERMANENT magnet? More science nonsense? :-)
Its not at all uncommon for a permanent magnet to loose its magnetic field, particualry after being dropped or exposed to heat.
@@ElectromagneticVideos Do ALL magnets loose some magnetism over time? Even neodymium? What if never used? Can a magnetic domain spontaneously move out of alignment?
@@MrSummitville Thats a very interesting question, particularity since we have have only been making magnets for the last few hundred years.
Iron containing rocks that have been heated have retained traces of the earths magnetic filed for thousands (millions?) of years, but those remnant fields are very weak. So magnetism can last a long time.
Magnet life is a probability thing: how strongly the domain boundaries are "locked" into place (based on the nature of the material the magnet is made of) and what forces/energy is available to help knock those boudaries loose so they can settle in a lower energy (lower total magnetism) state.
We constantly have thermal energy jiggling the domain walls with the occasional random big jiggle being enough to shift/release the weakest boundaries and therefor weakening the magnet. But after a short time all those weakest boundaries are moved and magnets tens to stabilize. Exposing a magnet to an opposing (repulsive) field provides more push to move those boundaries to reduce energy and reduce field so the thermal jiggling can now move some slightly better secured magnetic domain walls.
Bottom line: if the random max thermal "banging" of the magnetic domain walls + an opposing field exceeds how tightly the weakest magnetic domain walls are secured in place, the some domain walls will move and weaken the magnet.
In most controlled situations - not exceeding a certain temperature, vibration and opposing magnetic field, the magnetism will settle at a reasonable value (which can be very high as in neodymium example). A good example of this is magnets in an electric motor or loudspeaker in a car - very unfavourable place for a magnet but modern ones with materials designed for that do well.
So in the end after first magnetizing a magnet, its field will drop a bit but hopefully settle at a (good) level dictated by the environment it is subjected to or operated in.
Is there anything you can do to a magnet so that it will keep its magnetism longer?
Other than heating it up when you magnetize it I mean.
If you mean whne you are magnetizing it, no - assuming you are are already subjecting it to a good strong field. Howevern, once magnetized, there are a few things you can do to keep it nicly magnetized: 1) Put a steel bar or similar between the poles to make it "easier" for the B field to stay high on the BH curve 2) Dont subject the magnet to vibrations or shock 3) Keep it cool 4) Dont force it near an opposing magnetic field.
What I did leave out is all of this depends on the material the magnet is made out if some - some are more or less vulnerable to any of the items listed above.