Between both of your videos on the subject this is hands down the best intro on the internet. Even understanding the math there's no substitute for that simple physical intuition.
Both you guys are awesome at taking a complicated topic, breaking it down, explaining it in easy to understand terms. Thank you, and please keep up the great work!
I know I'm late to this party, but I just wanted to say, that this really helped me get over the initial information overload and gave me more questions than anything..... knowing how to search for the correct information and what terms are used / when different terms can and have been used interchangeably is a big help. Now I want to design some simple test circuits and get one of those little meters off Amazon! This looks like good fun, and something that could easily become more intuitive as I learn and experiment, to more deeply I understand the topic :)..... Between you and Tech Ingredients, I know I have learned more than I did in school, and you have tought countless others how to think and probblem solve the same. Thank you.
can you make a magnetic energy storage without super conductors? and could you use normal magnets as "springs" to store energy long term? also if diamagnetic materials are resistant to magnetic flow should we put diamagnetic materials on capacitors? i heard somewhere that the earths magnetic field is what drains most larger capacitors. Also since diamagnetic materials repell magnetic fields aren't they sort of working similarily to some types of superconductor in that field? How much study has there been into the conductivity of diamagnetic materials and are those 2 ways of repelling magnetic fields different? I've heard there are atleast 2 different types of superconductor floating in magnets one repels and one locks into the magnetic field. Could that locking be used as sort of "perfect" magnetic bridge that only "conducts" the magnetic "flow" in one direction?
Currently studying Electrical & Electronic Engineering at University so have come across a lot of different teaching styles and yours is clearly the best I've seen. Thank you for your public display of passion and ingenuity.
BH CURVE!!! THATS WHAT ITS CALLED!! Oh man, you have no idea how helpful this video was for me. I fly fpv racing quad copters which use really powerful brushless DC motors with really strong neodymium magnets in them.. Years ago I was discussing with a friend about how these motors wear out over time. Specifically, this friend was asking what the effect was of running the motors at really high voltage/current. I tried to explain to him how magnets are made by putting them in really strong electrical fields, and how when we use them to create rotational forces we are putting them in a similar electrical field, which as long as we stayed under a certain limit, we would get work out of the magnets, but the closer we got to the limit, the more the magnets would lose their *charge* so to speak. I remembered a little bit about the BH curve from high school physics, but for the life of me couldn't remember what it was called.
Congratulations for a great presentation! Although there was nothing new for me, I know I would not be able to present same things without the math. Here comes some of my personal “magnetics past”. Before I started my studies, I read some radio/electronics books and found there formulas to building a transformer necessary for the radio or other gear. There was this funny constant, 1.2 T. That was listed as a constant for the steel laminations and was used tu determine how many turns of wire was needed, along with some dimensional items and the frequency. O.K, my studies added all the hysteresis loss issues, plus Eddy Current losses to the story. And one thing that I learned was how to actually distinguish between the two kinds. Hysteresis losses increase proportional to the frequency, but Eddy current losses increase proportional to the square of the frequency. So, you measure the losses at two or more frequencies. I worked while studying and there I was introduced to Grain Oriented Steel that had saturation level indeed at 1.5 or even 1.7 T. But if you pushed your transformer design to those numbers, you started getting occasional trips of the breaker (or in our case blown fuses) and that with no load on the transformer. Why? That was because the inrush current brought the core into saturation depending on the exact moment of the AC voltage when the primary happened to be connected. The lower grade steel is more forgiving, as the hysteresis curve tails have a bit more slope or more rounded corner, while the grain oriented material settles on much flatter way or lower slope. Then, ferrite cores have much lower saturation limits than even the basic steels. My rule of thumb is that low frequency ferrites might be as much as 0.3 T, while high frequency applications I should not design with any higher than 0.1 T. I hope these small notes might still be digested by at least some viewers.
Pellervo Kaskinen hi , can you please explain difference between coupled inductors and transformer . I was studying about power electronics gate drive circuits where coupled inductors are used to isolate the high power and low power circuits . I thought it was just an isolation transformer but it was mentioned that it's called an pulse transformer. PS : I'm not afraid of math , if you could point me to any reading materials or sources about it , it would be great , Thank you.
Manoj Gowda - I may be on a wrong track, but my opinion about the difference is that the term “coupled inductors” came from people who tried to analyze the mathematics of it. The practical people just noticed the couple salient behaviors that implemented transformation of voltage and current and called the device a transformer. Then I have noticed that the term Coupled Inductors seems to be used on air core assemblies, or other cases where energy transfer is limited, including when the core operates into saturation. An example of such might be pulse transformer. On the other hand, you might consider what is called Tesla Coil - not Tesla Transformer. That at least as far as I have noticed. “Dear children have many names”.
How about those advanced Fe-Co alloys such as the Hiperco 50? They claim 2.2-2.4T saturation flux density when subjected to proper thermal annealing etc. Is this realistic?
you have a few significant mistakes: diamagnetic materials do NOT have negative permeabilities, just a lower slope than vacuum superconducting magnets do not overcome the issue of ferromagnetic saturation, they simply have a buttload of amp-turns brass has a permeability close to air, not zero
Applied Science I believe you may have been thinking of magnetic susceptibility and said permeability instead. For a perfect superconductor, magnetic susceptibility is -1 while magnetic permeability is 0. (Volumetric) Susceptibility is basically just the ratio between the M and H fields. χᵥ = M/H Permeability is the ratio between the B and H fields. μ = B/H For anyone reading who doesn't know; H is the applied magnetic field. M is the material's internal field due to H, (or magnetization) B is the total magnetic field, or essentially the sum of the H and M fields (except multiplied by the permeability of free space.) B = μ₀(H + M) (Edit: clarified volumetric susceptibility)
Diamagnetics don't have negative permeability? Dang, you just ruined my plans for a perpetual motion machine that pushes a wheel using an asymmetric magnetic field :O
"It's typically taught heavy on the math and theory". Unfortunately this seem to be the case on many subjects actually. Most students and interns I get who really don't have a clue what's going on. Excellent video!
Most academics prefer to copy paste notes from textbooks without putting the effort of showcasing applications where these principles are used. The sad thing is that institutions also don't care.
The fact that you so succinctly stated that "you don't really need to be exposed to the math until you actually need it" summarizes an immense problem in traditional education and open forums alike! Couldn't agree more, good sir. You are a saint among scholars.
I really appreciated this. I never could understand why nobody could just give a more layman's explanation of magnetic and I was not skilled enough on the subject to break it down for people as good as you have. It goes back years when I was first winding my first transformers, I was just looking for a little assistance on how many turns and how big my wire was just to get close to something that was functional, but instantly people are like, learn this 4th year college math and you can then try.
Drakkar Calethiel Same. Like Mr Carlson’s Lab. His can be over 2 hours often. And just like this. It’s no nonsense Fun. Pleasant to look at and listen to. Cheers.
It's not a simple subject, but Ben does a great job of staying on topic to explain the subject material. Ohm's Law can be demonstrated in under 10 minutes. Not so with magnetics!
I really keep coming back to this video every couple of months whenever magnets come up in any form. It's the best resource on magnetism on the whole of the internet.
I've been in electronics as a hobbiest for more than 30 years and even did some college courses in Electronics, and you surpassed any training I have had by a long shot in this one 50minute video! You are amazing! Keep up the good work I'm subscribing now!
50 minutes of quality, jam packed with easy to understand material and not a single time mention “subscribe, press the bell, like” and so on. Champion.
You're so great, man. I just love how straightforward, no non-sense and to the point your videos are, despite being quite long. I think I'd pick your channel as my favourite on YT if I had too.
I've been playing around with magnets for about 25 years now and I've figured out several of these things through trial and error... seeing the reasoning and math behind it is amazing. Thank you so much for the fantastic explanation!
I have never commented on a TH-cam video before, but I really appreciated all the work you put into this. Thanks for such a concise and practical intro, this outdid any university class I took on the subject and had was way more practical. Thanks again!
Thank you foryour way of explaining this complicated and hard to understand science of magnitism technology. I have been a electric motor rewind technician for 40 years, and been testing motor cores for flex densities,and core loss densities and never really understood the science of it until now. I just trusted our corel loss.machines calculations from the measured data i put into a coreloss tester,(lexco). I now have a better understanding of this part of my trade. Excellent job of explaining this complicated and confusing science.
I've been an IC design engineer for over 35 years and never really had to deal with actually understanding the magnetic concepts you have explained here. I often relied upon inductor data sheets to find the correct inductor for a switching power supply design. I cruised through BSEE design courses doing the math and not really understanding the magnetic properties that you are describing/educating in this video. Thank you for the beginnings of an intuitive understanding of the magnetic principles explained in this video. I say intuitive because the best designers can become very intuitive about understanding principles in a practical way so as to come up with designs or solutions to electrical problems. I know it's only a beginning lecture but it is the best beginning lecture I have ever had on magnetic principles, B Fields, H fields, magnetic flux and density etc etc. Thanks again.
Got a BSEE in the 1960s. I wish we had spent a day at this level of visualization and physical description. It would have made all the rest much clearer. Your presentation is reminiscent of Michael Faraday's papers--clear focus on physical observation and understanding rather than mathematics. Thanks. Glad I stumbled across your video.
What an excellent Magnetics crash course. I learn something new with EVERY video. Thank you. Please do a video on spectroscopy. How it works, how accurate it is, how to make one for cheap, software, ... There isn't any reputable video about it. I think it would be a valuable DIY tool to identify different LED claims, just to name one application. I am sure it would be handy anywhere spectroscopy is needed.
One of the best educational videos on magnetics! great Ben. I got one request could you make a small video on the simplest setup for getting BH curves. Your Oscilloscope is a grat way, but that might be out of reach for most of the hobbiest. So a cheap DIY measurement setup for measuring the BH curves and µ µr I think that would really help out a lot of people who are interested in this subject. Thanks
Thank you! I completely agree about a less expensive setup for measuring BH curves. In fact, there is a great solution: a single opamp can be setup to function as an integrator by placing a capacitor in the feedback loop. Typically a large (1 or 10M) resistor is placed in parallel with the capacitor to eliminate the problem of the integrator running away due to small DC offset voltages at the input. When measuring at 50/60Hz, almost any opamp will work. All you need in addition is a variac or other source of controllable AC, and an oscilloscope or data capture device. You can even use an older analog oscilloscope as long as it has X-Y mode (most of them do). I should have mentioned this in the video, since it may actually work a little better than using a scope's math function, and is the way that all these measurements were made before scopes with a math feature existed!
thanks for your comment, this is helpful for me. My ideal measurement setup would be something like a fixed geometry for a sample like a cylinder. (some magic equipment) and everything connected to the PC (via arduino perhaps). to get the data and calculate everything there.
If you are mostly interested in making the measurements themselves I'd recommend you get a USB oscilloscope. There's some available on eBay for around 70 $ (Hantek 6022BE, I don't know how good they are but the somewhat limited bandwidth of 20MHz should be fine for measurements like these) which are probably a lot easier to use than to setup an arduino. If you are more interested in setting it all up with an arduino then of course go ahead, just keep in mind that there are easier solutions. Cheers :)
how about a adafruit feather M0 (for better adc) or directly arduino if you don't worry for accuracy. A current transformer tied one end to a voltage divider, the other to your ADC in (load resistor also don't forget) or a hall current sensor from Allegro. Just measure them and plot them. Do the math inside the arduino and use PLOT to see the result or just use Labview and make it do everything.
Vale Sarbu there's still the risk of damaging the ADC of the arduino though if the voltage from the transformer gets too high. A solution would be a 5.1V zener diode connected from the ADC input to ground to make sure the measured voltage doesn't go above what the arduino can handle.
I love it when a plan comes together. This was one of those videos that my device played on it's own and one minute in I can't live without. A while back I was troubleshooting a golf cart charger and found a transformer with a swamping cap. Basically a design relying on the saturation magnetically of the material to regulate charge current. Not often a video is so good I have to pause it to comment, this is one of those. Thank you teacher, as always
Leave it Ben to upload a video on magnetics when I’m knee deep in magnets from every store and online source I could find right now 😎 I’m seriously in love with magnets right now
You videos are the best I saw for the physics insofar. Instead of diving in abstract math with no reasoning of 'why it should be like this' you give a real explanation of the phenomenon. There is no meaning in 'fields' and 'divergences' until you grasp a solid sense of reality in them. You provide it, and this is absolutely amazing. Please, please, continue this style of science exploration.
I probably absorbed more information about magnetics, and far more efficiently, in this singular video than in an entire semester at my community college. insanely well done
When I was a kid inductors seemed like magic to me. How could just a coil of wire be an electronic component. Years later when I studied electronic theory for my ham license it made more sense but it still didn't seem as concrete as Ohm's Law. Thank you for tying it all up into something that finally made sense.
Discovered the channel few days ago and now I have content to learn from for couple of months. Thank you for your dedication and effort you put in making these amazing videos. World is a better place because of people like you.
Thanks. While much more crude, I feel like I understood this stuff a little better after rewinding some transformers myself. (no content created on rewinding) I started playing with a couple of old phone chargers. I used the rated output, and voltage as a starting point. Then I took measurements of the open circuit voltage, and the actual voltage at the rated load current. Once I had that info, I removed the small transformer from the circuit, I boiled it in water to soften the varnish, and split the two halves of the core. The next step was to remove and count the secondary turns. It's tedious, but a necessary step. With the secondary turns ratio and the actual voltage/loaded current, I could calculate the primary turns ratio. This gave me the turns to voltage ratio. I used that number to wind a new secondary to whatever voltage I want. Of course I am aware that the secondary load determines the primary current, and I simply used the original wattage rating to determine the output capacity at whatever voltage I rewind the secondary for. I also used a thermal fuse incorporated just outside the secondary winding as an extra safety measure in these crude experiments. These devices are not intended to be left powered and unattended for any reason. That said I still have a couple of old 5v chargers that put out 9 and 12 volts. I also built one that does +/-5. Those experiments got me thinking about trying to rewind some standard 60hz mains transformers. I've rewound 2 of them so far with the same results, although rewinding a little 12volt 1 amp mains secondary is a chore compared to a little SMPS. For a person without the academic background like myself a practical and simple experience like this helped me see through the jargon and math well enough to help me want to learn more. I would love to be able to clearly test and measure saturation in a core. I have saved many examples in playlists (that are publicly listed too if anyone is exploring EE on YT), including saving this upload in my "Fundamentals Power Supply" playlist. I shelved my transformer experiments a few months ago, but I think the next step for me will be building a tesla meter. I think a project like that will really help me to connect the dots. I'm just trying to share a bit of the learning experience from the perspective of someone that is interested and engaged in the subject, but lacks the rigorous EE background to make sense of these things. As far as the stupid terminology used in the field. I personally find it really annoying. Humanity needs an international Scientific version of ANSI to modernize a lot of the poorly organized, antiquated, and grandfathered terminology that could and should be eliminated in favor of intuitive solutions. Some people say it's too hard to change, but the saying, "it will never be easier than it is right now" always applies. That's just my $0.002 adsense. -Jake
I agree everything except the new terminology part, I think with some academic background, you can understand them. Ben's videos are awesome, most of the time, stuff is not thought with this level of emphasis on practical measurement. I actually sent this video to my professor.
"It's much better to keep things conceptual until you really need the math for some specific reason" - This is >the way< to learn for me. Thank you so much for helping me visualize and simulate "magnetics" on my mind.
When I saw the brushless outrunner in the upper corner near the video's end, I hoped you might mention how electromagnetic flux is turned into rotary motion. What do you think about producing a video on the common types of electromagnetic motors? Induction motors, permanent magnet motors, switched reluctance motors, and the new breed: hybrid permanent magnet - switched reluctance motors? Thank you so much for a great video, I think I know more about reluctance, coercivity, and their relationship with alternating frequency than when I started!
Ben - Thank you. This video was tuned perfectly not only to my existing grasp of electronics, but also the way that I learn. I can do math, but I don't think in math, and thus since electronics is only a hobby for me, magnetics have always remained a subject of blurry black magic where I don't know and can't understand one of these variables from another. I think I retained about 1/2 to 2/3 of the material here on the first pass, so, that's about 99% more than I ever have before. One of the biggest problems in education in my opinion is that usually the people who understand something the best, are the worst to teach it because they just intuitively got it. They don't know how to think like someone who doesn't just instantly get it. Or, people who learned something at a high level giving a simplified high-level explanation rather than an actual introductory explanation. So a lot of sciency fields end up dominated by people preaching to their choirs, using only the explanations that they understood themselves when they learned it, kind of like an unnecessary gatekeeping as if they insisted on teaching the class in latin. Don't already understand latin? Oh well, guess you don't get to learn calculus/magnetics/optics/etc either. There are very, very few people in the world who break down these barriers. I'd say this is probably the best laymen's explanation of magnetics available to the public, so, thank you for adding something unique to the world.
Awesome! This explained so much, by providing a more intuitive framework, and connecting it to what I already know about electric circuits. Thank you so much!
This is the video I've been waiting for. Nobody on the easily googled internet explains things like how magnetic flux is able to be "conducted"- this finally explains why you can lift a bunch of paperclips on end with a strong magnet, but can hardly affect one from the same distance away as the paperclip ladder was long. Thanks
Thanks for the video, Ben! I'm super thankful for some of the newer magnetic scale systems that the chinese have developed which accomodate a greater range and resolution of values.
I now understand what the "permeability of empty space" refers to in physics charts. Thank you. This constant comes up all the time in my Wikipedia deep dives and I've never been able to make sense of it.
Wow, great video! I see your approach is a little bit different from what is typically used, at university we started with fundamentals and gradually came to materials and stuff, yours is very easy to understand nevertheless. Here's a few suggestions: when measuring BH curve with an oscilloscope and secondary winding, you could just use RC integrator instead of mathematical function, that would be simpler and I guess more availible to most of your viewers; also it would be very interesting to see a BH curve of a permanent magnet, as far as I understand it's almost rectangular for these kinds of materials.
I am preparing to start a job where we manufacture the large cables that're used in MRI machines. My understanding of basic engineering topics is sound, however due to my particular learning style (as well as personal need to review and revise my subject learning, even when I know it very well), I've been searching for some videos to help get me started. I must commend you for your teaching style and organization. I can't tell you how many professors teach without context or relating it to practical uses (like how it'll apply to the real world), and even in basic discussions with my classmates, we don't really understand how to explain the why, but are adequate in performing the math. Thanks near solely to this video, I've managed to get a great baseline on the topic of magnetism, and applying it to my job. A genuine thank you, as well as plea to future teachers: Use this teaching style as inspiration. There are many different ways to teach a topic, but regardless with how you feel about it, people are becoming far more visual learners who need direct applications, rather than baseless equations and dry math.
This is one of the best magnetics introductions I've ever seen. It is so easy to get loose on math and be disconnected from the physics behind. When I learnt this on my second year of EE, I was able to solve exercises so I passed,, next year I was an teaching assistant, and then I started to understand. Finally truogh labs classes and a few years I got enough physical understanding. Today I think that some lab should be done in advance to the hard math/physics teaching so an integral is not a math challenge but a sum, a divergent is really a measure of something real diverting, and so on.
I did my big delve into transformer design half a decade ago and have learned since, but I'm still going into this excited. Have you read about the team that used superconductors to make legitimate "wires" for near lossless magnetic field transportation? It was still only lab work when I read about it. I hope more work has been done on that, it was very fascinating.
I thought that magnetic fields are the arch enemy of superconductors. I can remember "glass iron" (extremly fast cooled iron), which had excellent magnetic proprieties for transformers...
it's true that superconductors have a critical flux density beyond which the superconducting state is destroyed and the magnet is quenched, but it is very high for the perovskite high-temperature superconductors like YBCO. This is why advanced YBCO tapes are being used in the next generation compact tokamak fusion reactors currently under construction like MIT's ARC design and Tokamak Energy's ST40 compact spherical tokamak. th-cam.com/video/NuiQTDanHx0/w-d-xo.html
I have to agree that this is a very good educational video. Just a few remarks. When talking about the saturation you should mention that the curve does not turn horizontal up there but continues with the slope of the permeability of free space. Your text notes are too small to be read on a screen.
@42min your small toroidal ferrite "transformer" is a filter coil meant to filter out high-frequency disturbances from a mains supply by passing phase an neutral through the two windings.
Sorry, its not a Rule. its a convenience. - and entirely dependent on the resistance of the wire. - EG. you can have unlimited turns, if you have superconductor wire. like iridium alloy. - oh and you can just use litz wire copper also
lol yes, newman was terrible at demonstrations. - he took the theory in the other direction with tiny wire, too choke the current. - 50,000 turns for 2 watts input, - -- ,it has too move something rite ? , even with huge magnets... this proves even our electrical intuition is better than "amps times turns" - that's physics!
I've studied engineering and physics. As such, I've covered this content in substantial detail and yet this short video was equally as useful in providing the INTUITION about magnetism as the countless hours of theoretical work I've done. Obviously for professional application of this technology, the theoretical knowledge is indispensable, but for the sheer joy of science, the INTUITION is all that is required.
Hi Ben! Great video. One question though... I thought that the residual magnetic field that remains after the external field is removed is called the magnetic remanence, not the coercivity. The coercivity is the strength of the external field necessary to cause the material to become magnetized, a measurement of "magnetic hardness". Once the material is magnetized and the external field is removed, the strength of the residual field depends on the remanence of the material. Did I misunderstand something? (I've only watched the video once so far...)
I think you are absolutely correct! In fact, it's been a long time since I've heard the word remanence, and since the two properties often go together, I forget they are in fact separate points on the BH curve. Thanks for pointing this out!
I was going to say that but luckily I searched for 'remanence' first :-) Also, the energy it takes to drive the magnetisation per cycle is effectively the area of the BH curve, so that is a handy guide when testing junk-box coils. 50/60Hz current transformer construction is fun, I had to order special low coercivity toroids for a power-tool monitor that auto-triggered a shop-vac. I find these tools handy - www.mag-inc.com/Design/Design-Tools
I like this part of Ben: when he muffs something (very easy to do on a subject like this), he admits it, and that's it. There's no shame in it. Stuff happens. Lord knows I have made a lot of errors in my professional life. All science and engineering practitioners should be like Ben.
I seem to recall _remanence_ also being called _retentivity,_ which seems a more descriptive term... though with 5 short syllables, it is a bit of a tongue-twister. At least retentivity will not be confused with _revenants!_ en.wikipedia.org/wiki/Revenant
At 48:17. The problem is..." You can't always get everything that you want. but, you can get what you need!" 😊 👍 I think that I have heard that before. Thank you for a great video!
Watched this video again the 3rd time. I had some old copper ballasts that were being scraped in my apartment lighting (after 7 years of running) and being replaced with electronic ballasts. I collected them and planning to do some experiment. Your video comes very handy and practical.
The energy that's put into a permanent magnet at its time of manufacture, where does that energy go when you heat the magnet to its Curie point? Is it converted to heat then lost to space by radiation/conduction?
No energy is stored in permanent magnets, thats an illusion. example: Take a jar of pennies, reorder every pennies in the jar so the face point upward, this takes energy. Now, shake that jar, did the pennies get warmer bc they are now randomly oriented? No Edit: Permanent magnet are made out of "magnetic" atoms, the magnetization just align the atoms (cluster of) in one direction, this rotations heat up the magnet while it's manufactured. Heating over its Curie point, just randomize the atoms back.
MrJimbo1qaz yes, if you try to put two of the same poles together you will feel the force pushing the poles away. If you keep the poles together you are putting in work to counter the magnetic force. Work is the transfer of energy and has the same units.
This is possibly the best youtube tutorial I have ever watched. I wish this had been available all those years ago to watch before lecture 1 of my Uni Electromagnetics course!
RJ Anderson This was one of the best explanations of the fundamentals. There are quite a few older videos that I've come across that demonstrate the subject of magnetics as they relate to transformers/electronics. I have saved everything I've come across over the last few years in playlists. Originally they were all private and simply intended as a form of personal reference. A few months ago I decided to make them all public along with my subscriptions list. (I'm not monetized, I have no intention of changing that, and I really don't care if anyone checks out what I've done. I have nothing to gain.) The reference is just intended as another FOS'y source for anyone that is interested. I have a playlist called "Fundamentals Power Supply." About halfway down that playlist are a few videos from a CC called Eric Goodchild. IIRC he goes into this subject really well and built a saturation measurement device. Old videos like this are hard to find on YT as the SEO of YT is setup to heavily bias new and/or monetized content. I don't hold monetization against anyone IMO. It's their right as a CC and I respect that. However, there are a lot of channels from brilliant people who decide they do not want to monetize and do not upload regularly. Sometimes it can be difficult to find them. Stay Curious ;) -Jake
As someone coming from a Physics background my study of E&M (and magnetics in particular) was always centered around behavior in vacuum, with material considerations always rushed through without much depth or consideration. Seeing a systematic treatment of magnetic behavior in materials analagous to electric behavior in materials (electric circuits) has done a lot to remedy my aversion to "practical" electromagnetism in such a short time. Really well done.
Here comes the much-needed video. There is not enough content on Magnetics available on youtube, this video comes to fill that gap. I also liked that fact that it is a long video. I love detailed videos.
Here is a confession for you sir: I am about to finish my Bsc in physics, I am Major in physics and minor in mathematics. I always viewed experimentalists as those whom their job is just the repetition of the same process (Do 1 2 3 take data then the next day do the same thing). I hated experiments in the University to be honest! Not that I actually hated them, I just thought what they are all the same thing, I would rather take a pen and a paper and solve equations rather than repeating the same thing everyday for the rest of my life. Now, I think I know what is the problem. Experiments are not fun in doing them, they are fun in building and debugging them. They are like a programing code, you will have fun building and debugging a code "say a calculator", but you will probably not have fun using it to calculate things. You inspired me sir, I am going to apply for theoretical and mathematical physics PhD next year!
Funny, your view of experiments is my view of theory (as it's commonly done in physics, computer science is somewhat different and more clear): why solve the same equations and the same (type of) proofs over and over again, yet learn nothing in any depth, if you look at it honestly. I think the real difference is how much creativity and insights you gain during the process, while reducing the frustration factor involved with "tooling" issues. The tools in theoretic problems, are mastering the theoretical concepts and math that are usually pretty remote from the topic itself and often have quirky formulations.
Uh okay. I love theory because I don't solve the same problems over and over again! I don't like any course in my program LOL. I love the subjects but not the exams nor the ways of teaching. (I research what I like in the subject, and a lot of the time I learn it by myself from various sources) So, I think we hate theories and experiments because of the methodology of teaching. Just to tell you how I fell in love with theory: 1- Find a research project of interest. Something you really don't mind investing a year in reading and studying. 2- Find good and multiple sources. 3- Ask and discuss others.
I've already watched this video a few times since you released it. But man this is so information dense, I could watch it dozens of times and still keep learning stuff. It's like the educational version of something like The Simpsons is with humour. It's so densely packed that you find new things every time you watch it. Or just old things you forgot about.
It’s definitely taught heavy on the math. Spent the whole semester deriving equations and didn’t remember much. It wasn’t until presentations like this came along that it all clicked. There was definitely value in deriving those equations, it just took a 15 years to put it all together. Thank you.
There's a channel by a guy named Jeff Quigley I think it's spelled...he posts a lot of old BandW videos about electronics and magnetics that are 1950's Navy productions...pretty interesting.
This is incredible. I did fall asleep a couple of times but that's me.. I used to miss half the lessons back in Engineering school. But with TH-cam I wake back up and go back. Thanks for such hard work to tech us so much !! Your channel is amazing.
Applied Science The wooden wedge-based handling techniques that brainiac75(?) has developed for the contact and separation of big magnets are really interesting and effective.
I've had a love affair with magnets and magnetism for somewhere in the neighborhood 50 years, read a lot about magnets and this video does a good job of summing it up. Great job one of your best video yet. Thanks
If you have wire wound around an iron core, and at a given current it is saturated, if you pass a higher current through the wire, what happens to that extra magnetic field or flux that is being generated?
Good question. Once saturated, any additional H caused by additional current in the coil will behave as if the iron didn't exist at all. It will spread out through the air just as it would without the iron. It would be nice if the transition through saturation were like a brick wall -- snapping into a new regime suddenly. If this were the case, we could first measure the field caused by 100% saturation, then measure the field caused by air (with the iron core removed), and then sum them together. In the real world, the transition to saturation is gradual, and the field making its way outside the core will interact with the partially saturated core, and cause things to become a little more messy.
The phenomenon you are looking for is called magnetic flux leakage. The magnetic field will literally leak out of the iron core and start flowing through the air around the core instead.
Magnetically, it would make the field weaker but would make very little difference overall. Your essentially shorting out a small section of the magnetic field. Remember that flowing electrons create a circular magnetic field that flows around the current flow. So the magnetic properties of the wire aren't very significant, it's whats around the wire that has the most impact. Electrically on the other hand, by using wire with a higher resistivity, you've increased the resistance of the coil. Which means you need more voltage to have same amount of current flowing through the coil. This means you will need to have more input power to produce the same magneto-motive force and your overall efficiency would drop.
I have had this on my watch list for six months or more, because i knew it was going to be a ton of information to absorb, and I needed to be ready. Wow, it was excellent, and I'm glad I didn't give up! I want to rewatch it after my brain cools down.
The green thing u shown in the beginning through which we can see magnetic field lines of magnetic. Please tell the name of that thing. And from where can we purchase it?
A well explained and easy to understand breakdown of the working principles, definitions, units, terms, plus other aspects which make up this complex subject, that even after 35 years as an electronics technician I still have trouble with. Thanks so much for sharing. 😉👌🏻
this is what electrical machine classes should look like before the lectures go through all the theory behind it and hard to solve maxwell equations , this give u better idea of this principle and make you understand all the maths and theory . nice presentation
You are such a good teach my man. An amazing balance between almost kindergarten "hands on experiments", human intuition and college level theory. I feel like anyone who didn't follow everything, could easily google the tiny missing bit, then come back and be good to go.
If you put a highly diamagnetic material in place of the air gap, would you get a net negative reluctance? And what would that do to the magnetic field flowing in the "circuit"?
I was wrong about this in the video. One of the other commenters helpfully pointed out that diamagnetic materials do not have negative permeability, but rather a permeability that is lower than empty space. This means that in an H field, the material will conduct magnetic flux more poorly than empty space itself). The magnetic field lines will partially flow around the diamagnetic material instead of through it because the material poses slightly more reluctance than the space around it. A compass needle aligns itself with the magnetic field, while a piece of diamagnetic material will become perpendicular to the field lines.
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Wow! It isn't often that I watch a video several times, but this may be the best presentation of magnetic principles I have ever seen. Thanks!
Thanks! That means a lot coming from someone like you!
Between both of your videos on the subject this is hands down the best intro on the internet. Even understanding the math there's no substitute for that simple physical intuition.
Both you guys are awesome at taking a complicated topic, breaking it down, explaining it in easy to understand terms. Thank you, and please keep up the great work!
I know I'm late to this party, but I just wanted to say, that this really helped me get over the initial information overload and gave me more questions than anything..... knowing how to search for the correct information and what terms are used / when different terms can and have been used interchangeably is a big help. Now I want to design some simple test circuits and get one of those little meters off Amazon! This looks like good fun, and something that could easily become more intuitive as I learn and experiment, to more deeply I understand the topic :)..... Between you and Tech Ingredients, I know I have learned more than I did in school, and you have tought countless others how to think and probblem solve the same. Thank you.
A wonderful concise, comprehensive explanation of magnetism and its measurements! Thank you
You condensed an entire course in transformer design and magnetism in about an hour. Well done, really informative.
transformer design is much more complicated... and it's like a kind of black magic :-)
this video is just "rookie course" of magnetism
Also a tremendous class of didactics.
This is such a good presentation of the topic. Really appreciate the effort that went into this video. I learned a lot.
Thank you!
Practical Engineering your also too good at explanation. I went through your videos.
therealnightwriter .
I agree. Thanks for the effort!
can you make a magnetic energy storage without super conductors? and could you use normal magnets as "springs" to store energy long term? also if diamagnetic materials are resistant to magnetic flow should we put diamagnetic materials on capacitors? i heard somewhere that the earths magnetic field is what drains most larger capacitors.
Also since diamagnetic materials repell magnetic fields aren't they sort of working similarily to some types of superconductor in that field?
How much study has there been into the conductivity of diamagnetic materials and are those 2 ways of repelling magnetic fields different?
I've heard there are atleast 2 different types of superconductor floating in magnets one repels and one locks into the magnetic field. Could that locking be used as sort of "perfect" magnetic bridge that only "conducts" the magnetic "flow" in one direction?
In less than an hour, you gave me a better understanding than a 5-week segment of my physics course 👍
Currently studying Electrical & Electronic Engineering at University so have come across a lot of different teaching styles and yours is clearly the best I've seen. Thank you for your public display of passion and ingenuity.
BH CURVE!!! THATS WHAT ITS CALLED!! Oh man, you have no idea how helpful this video was for me. I fly fpv racing quad copters which use really powerful brushless DC motors with really strong neodymium magnets in them.. Years ago I was discussing with a friend about how these motors wear out over time. Specifically, this friend was asking what the effect was of running the motors at really high voltage/current. I tried to explain to him how magnets are made by putting them in really strong electrical fields, and how when we use them to create rotational forces we are putting them in a similar electrical field, which as long as we stayed under a certain limit, we would get work out of the magnets, but the closer we got to the limit, the more the magnets would lose their *charge* so to speak. I remembered a little bit about the BH curve from high school physics, but for the life of me couldn't remember what it was called.
Congratulations for a great presentation!
Although there was nothing new for me, I know I would not be able to present same things without the math.
Here comes some of my personal “magnetics past”. Before I started my studies, I read some radio/electronics books and found there formulas to building a transformer necessary for the radio or other gear. There was this funny constant, 1.2 T. That was listed as a constant for the steel laminations and was used tu determine how many turns of wire was needed, along with some dimensional items and the frequency. O.K, my studies added all the hysteresis loss issues, plus Eddy Current losses to the story. And one thing that I learned was how to actually distinguish between the two kinds. Hysteresis losses increase proportional to the frequency, but Eddy current losses increase proportional to the square of the frequency. So, you measure the losses at two or more frequencies.
I worked while studying and there I was introduced to Grain Oriented Steel that had saturation level indeed at 1.5 or even 1.7 T. But if you pushed your transformer design to those numbers, you started getting occasional trips of the breaker (or in our case blown fuses) and that with no load on the transformer. Why? That was because the inrush current brought the core into saturation depending on the exact moment of the AC voltage when the primary happened to be connected. The lower grade steel is more forgiving, as the hysteresis curve tails have a bit more slope or more rounded corner, while the grain oriented material settles on much flatter way or lower slope.
Then, ferrite cores have much lower saturation limits than even the basic steels. My rule of thumb is that low frequency ferrites might be as much as 0.3 T, while high frequency applications I should not design with any higher than 0.1 T. I hope these small notes might still be digested by at least some viewers.
Pellervo Kaskinen hi , can you please explain difference between coupled inductors and transformer . I was studying about power electronics gate drive circuits where coupled inductors are used to isolate the high power and low power circuits . I thought it was just an isolation transformer but it was mentioned that it's called an pulse transformer.
PS : I'm not afraid of math , if you could point me to any reading materials or sources about it , it would be great , Thank you.
Manoj Gowda - I may be on a wrong track, but my opinion about the difference is that the term “coupled inductors” came from people who tried to analyze the mathematics of it. The practical people just noticed the couple salient behaviors that implemented transformation of voltage and current and called the device a transformer.
Then I have noticed that the term Coupled Inductors seems to be used on air core assemblies, or other cases where energy transfer is limited, including when the core operates into saturation. An example of such might be pulse transformer. On the other hand, you might consider what is called Tesla Coil - not Tesla Transformer. That at least as far as I have noticed. “Dear children have many names”.
Pellervo Kaskinen thanks 👍
How about those advanced Fe-Co alloys such as the Hiperco 50? They claim 2.2-2.4T saturation flux density when subjected to proper thermal annealing etc. Is this realistic?
Awesome comment.
you have a few significant mistakes:
diamagnetic materials do NOT have negative permeabilities, just a lower slope than vacuum
superconducting magnets do not overcome the issue of ferromagnetic saturation, they simply have a buttload of amp-turns
brass has a permeability close to air, not zero
Whoops! Thanks for pointing this out!
Applied Science I believe you may have been thinking of magnetic susceptibility and said permeability instead. For a perfect superconductor, magnetic susceptibility is -1 while magnetic permeability is 0.
(Volumetric) Susceptibility is basically just the ratio between the M and H fields. χᵥ = M/H
Permeability is the ratio between the B and H fields. μ = B/H
For anyone reading who doesn't know;
H is the applied magnetic field.
M is the material's internal field due to H, (or magnetization)
B is the total magnetic field, or essentially the sum of the H and M fields (except multiplied by the permeability of free space.) B = μ₀(H + M)
(Edit: clarified volumetric susceptibility)
Wew I wondered how u guys understand this nerdy thing (oh well guess u guys are nerds too)
Diamagnetics don't have negative permeability? Dang, you just ruined my plans for a perpetual motion machine that pushes a wheel using an asymmetric magnetic field :O
Is a buttload a CGS unit or SI?
"It's typically taught heavy on the math and theory". Unfortunately this seem to be the case on many subjects actually. Most students and interns I get who really don't have a clue what's going on.
Excellent video!
It's expected to be known, not reaaally explained in depth at all.. Just the formulas are given.
Most academics prefer to copy paste notes from textbooks without putting the effort of showcasing applications where these principles are used. The sad thing is that institutions also don't care.
The fact that you so succinctly stated that "you don't really need to be exposed to the math until you actually need it" summarizes an immense problem in traditional education and open forums alike! Couldn't agree more, good sir. You are a saint among scholars.
Really nice practical review of a deceptively complex topic!
I really appreciated this. I never could understand why nobody could just give a more layman's explanation of magnetic and I was not skilled enough on the subject to break it down for people as good as you have. It goes back years when I was first winding my first transformers, I was just looking for a little assistance on how many turns and how big my wire was just to get close to something that was functional, but instantly people are like, learn this 4th year college math and you can then try.
50 minute long video? Exactly what I love!
haha, I was just thinking the same thing. "A 50 minute Applied Science video? You know it's gotta be good!"
Drakkar Calethiel Same. Like Mr Carlson’s Lab. His can be over 2 hours often. And just like this. It’s no nonsense
Fun. Pleasant to look at and listen to.
Cheers.
It's not a simple subject, but Ben does a great job of staying on topic to explain the subject material. Ohm's Law can be demonstrated in under 10 minutes. Not so with magnetics!
I really keep coming back to this video every couple of months whenever magnets come up in any form. It's the best resource on magnetism on the whole of the internet.
I've been in electronics as a hobbiest for more than 30 years and even did some college courses in Electronics, and you surpassed any training I have had by a long shot in this one 50minute video! You are amazing! Keep up the good work I'm subscribing now!
50 minutes of quality, jam packed with easy to understand material and not a single time mention “subscribe, press the bell, like” and so on. Champion.
Holy hell what a scope!
I was drooling over that as well. Those scopes are north of $20K.
2 GHz, 8 analog or 64 digital channels. Juicy.
I was salivating too !!!
Reichert Zetopan are you guys Subs of Mr Carlson’s lab. Just curious. I assume you all are.
@Reichert Zetopan Now I know why the teachers were always so shit scared of letting us use them at College. I had no idea they could cost so much!
I watch this every now and again. It's a great break down of the BH curve and helps give a bit of an insight into magnetics. Thank you very much.
You're so great, man. I just love how straightforward, no non-sense and to the point your videos are, despite being quite long. I think I'd pick your channel as my favourite on YT if I had too.
I've been playing around with magnets for about 25 years now and I've figured out several of these things through trial and error... seeing the reasoning and math behind it is amazing. Thank you so much for the fantastic explanation!
I have never commented on a TH-cam video before, but I really appreciated all the work you put into this. Thanks for such a concise and practical intro, this outdid any university class I took on the subject and had was way more practical. Thanks again!
Thank you foryour way of explaining this complicated and hard to understand science of magnitism technology. I have been a electric motor rewind technician for 40 years, and been testing motor cores for flex densities,and core loss densities and never really understood the science of it until now. I just trusted our corel loss.machines calculations from the measured data i put into a coreloss tester,(lexco). I now have a better understanding of this part of my trade. Excellent job of explaining this complicated and confusing science.
I've been an IC design engineer for over 35 years and never really had to deal with actually understanding the magnetic concepts you have explained here. I often relied upon inductor data sheets to find the correct inductor for a switching power supply design. I cruised through BSEE design courses doing the math and not really understanding the magnetic properties that you are describing/educating in this video. Thank you for the beginnings of an intuitive understanding of the magnetic principles explained in this video. I say intuitive because the best designers can become very intuitive about understanding principles in a practical way so as to come up with designs or solutions to electrical problems. I know it's only a beginning lecture but it is the best beginning lecture I have ever had on magnetic principles, B Fields, H fields, magnetic flux and density etc etc. Thanks again.
This video was pure gold. Thanks.
not sure if that's a compliment or an insult based on the magnetic properties of gold ;-)
Thank you. that was brilliant specially the emphasis on the fact the the B-H curve characteristics is frequency dependent.
Was going to watch a movie but a nearly hour long video here, much better!
Got a BSEE in the 1960s. I wish we had spent a day at this level of visualization and physical description. It would have made all the rest much clearer. Your presentation is reminiscent of Michael Faraday's papers--clear focus on physical observation and understanding rather than mathematics. Thanks. Glad I stumbled across your video.
What an excellent Magnetics crash course. I learn something new with EVERY video. Thank you.
Please do a video on spectroscopy. How it works, how accurate it is, how to make one for cheap, software, ...
There isn't any reputable video about it.
I think it would be a valuable DIY tool to identify different LED claims, just to name one application.
I am sure it would be handy anywhere spectroscopy is needed.
Excellent video, and it's so nice to see a lot of my other favorite channels commenting on this video.
One of the best educational videos on magnetics! great Ben. I got one request could you make a small video on the simplest setup for getting BH curves. Your Oscilloscope is a grat way, but that might be out of reach for most of the hobbiest. So a cheap DIY measurement setup for measuring the BH curves and µ µr I think that would really help out a lot of people who are interested in this subject. Thanks
Thank you! I completely agree about a less expensive setup for measuring BH curves. In fact, there is a great solution: a single opamp can be setup to function as an integrator by placing a capacitor in the feedback loop. Typically a large (1 or 10M) resistor is placed in parallel with the capacitor to eliminate the problem of the integrator running away due to small DC offset voltages at the input. When measuring at 50/60Hz, almost any opamp will work. All you need in addition is a variac or other source of controllable AC, and an oscilloscope or data capture device. You can even use an older analog oscilloscope as long as it has X-Y mode (most of them do). I should have mentioned this in the video, since it may actually work a little better than using a scope's math function, and is the way that all these measurements were made before scopes with a math feature existed!
thanks for your comment, this is helpful for me. My ideal measurement setup would be something like a fixed geometry for a sample like a cylinder. (some magic equipment) and everything connected to the PC (via arduino perhaps). to get the data and calculate everything there.
If you are mostly interested in making the measurements themselves I'd recommend you get a USB oscilloscope. There's some available on eBay for around 70 $ (Hantek 6022BE, I don't know how good they are but the somewhat limited bandwidth of 20MHz should be fine for measurements like these) which are probably a lot easier to use than to setup an arduino. If you are more interested in setting it all up with an arduino then of course go ahead, just keep in mind that there are easier solutions. Cheers :)
how about a adafruit feather M0 (for better adc) or directly arduino if you don't worry for accuracy. A current transformer tied one end to a voltage divider, the other to your ADC in (load resistor also don't forget) or a hall current sensor from Allegro. Just measure them and plot them. Do the math inside the arduino and use PLOT to see the result or just use Labview and make it do everything.
Vale Sarbu there's still the risk of damaging the ADC of the arduino though if the voltage from the transformer gets too high. A solution would be a 5.1V zener diode connected from the ADC input to ground to make sure the measured voltage doesn't go above what the arduino can handle.
I love it when a plan comes together. This was one of those videos that my device played on it's own and one minute in I can't live without. A while back I was troubleshooting a golf cart charger and found a transformer with a swamping cap. Basically a design relying on the saturation magnetically of the material to regulate charge current. Not often a video is so good I have to pause it to comment, this is one of those. Thank you teacher, as always
Leave it Ben to upload a video on magnetics when I’m knee deep in magnets from every store and online source I could find right now 😎 I’m seriously in love with magnets right now
learnt more than my 4yrs of degree.... that says a lot about the quality of my degree classes & the quality of the video.... thanks you for this 🙏
Excellent presentation! I like the old analog ammeter, it reminds me of the panel meters/gauges I saw in my abandoned US military base videos.
I have the bigger version of it. I bought mine at a antique store but you can find them on eBay pretty cheap!
You videos are the best I saw for the physics insofar. Instead of diving in abstract math with no reasoning of 'why it should be like this' you give a real explanation of the phenomenon. There is no meaning in 'fields' and 'divergences' until you grasp a solid sense of reality in them. You provide it, and this is absolutely amazing. Please, please, continue this style of science exploration.
This is amazing! Really understandable for someone as uneducated about this as I was. I love all your teaching videos, keep it up!
I feel like I've learned more about electromangetism in about 50 minutes than I've learned in years of study. Thank you very much for the great video!
Hi Ben, you are my hero. That is all.
fun to watch gifted people.
I probably absorbed more information about magnetics, and far more efficiently, in this singular video than in an entire semester at my community college. insanely well done
This is so incredibly amazing. Wish there were more videos like this on TH-cam
When I was a kid inductors seemed like magic to me. How could just a coil of wire be an electronic component. Years later when I studied electronic theory for my ham license it made more sense but it still didn't seem as concrete as Ohm's Law. Thank you for tying it all up into something that finally made sense.
39:14 This works as a transformer, but it's probably intended to be a common mode choke - for EMI suppression.
Discovered the channel few days ago and now I have content to learn from for couple of months. Thank you for your dedication and effort you put in making these amazing videos. World is a better place because of people like you.
Thanks. While much more crude, I feel like I understood this stuff a little better after rewinding some transformers myself. (no content created on rewinding)
I started playing with a couple of old phone chargers. I used the rated output, and voltage as a starting point. Then I took measurements of the open circuit voltage, and the actual voltage at the rated load current. Once I had that info, I removed the small transformer from the circuit, I boiled it in water to soften the varnish, and split the two halves of the core. The next step was to remove and count the secondary turns. It's tedious, but a necessary step. With the secondary turns ratio and the actual voltage/loaded current, I could calculate the primary turns ratio. This gave me the turns to voltage ratio. I used that number to wind a new secondary to whatever voltage I want.
Of course I am aware that the secondary load determines the primary current, and I simply used the original wattage rating to determine the output capacity at whatever voltage I rewind the secondary for. I also used a thermal fuse incorporated just outside the secondary winding as an extra safety measure in these crude experiments. These devices are not intended to be left powered and unattended for any reason. That said I still have a couple of old 5v chargers that put out 9 and 12 volts. I also built one that does +/-5.
Those experiments got me thinking about trying to rewind some standard 60hz mains transformers. I've rewound 2 of them so far with the same results, although rewinding a little 12volt 1 amp mains secondary is a chore compared to a little SMPS.
For a person without the academic background like myself a practical and simple experience like this helped me see through the jargon and math well enough to help me want to learn more. I would love to be able to clearly test and measure saturation in a core. I have saved many examples in playlists (that are publicly listed too if anyone is exploring EE on YT), including saving this upload in my "Fundamentals Power Supply" playlist.
I shelved my transformer experiments a few months ago, but I think the next step for me will be building a tesla meter. I think a project like that will really help me to connect the dots.
I'm just trying to share a bit of the learning experience from the perspective of someone that is interested and engaged in the subject, but lacks the rigorous EE background to make sense of these things.
As far as the stupid terminology used in the field. I personally find it really annoying. Humanity needs an international Scientific version of ANSI to modernize a lot of the poorly organized, antiquated, and grandfathered terminology that could and should be eliminated in favor of intuitive solutions. Some people say it's too hard to change, but the saying, "it will never be easier than it is right now" always applies. That's just my $0.002 adsense.
-Jake
I agree everything except the new terminology part, I think with some academic background, you can understand them. Ben's videos are awesome, most of the time, stuff is not thought with this level of emphasis on practical measurement. I actually sent this video to my professor.
"It's just one of those constants. It's the way the universe works. It's just there."
I LOVE it!
Back to bingeing on your videos.
Great stuff!
Your ability to explain concepts simply and thoroughly is amazing. Thank you for the effort you put into your content to make it excellent.
"It's much better to keep things conceptual until you really need the math for some specific reason" - This is >the way< to learn for me. Thank you so much for helping me visualize and simulate "magnetics" on my mind.
When I saw the brushless outrunner in the upper corner near the video's end, I hoped you might mention how electromagnetic flux is turned into rotary motion. What do you think about producing a video on the common types of electromagnetic motors? Induction motors, permanent magnet motors, switched reluctance motors, and the new breed: hybrid permanent magnet - switched reluctance motors? Thank you so much for a great video, I think I know more about reluctance, coercivity, and their relationship with alternating frequency than when I started!
One of the most valuable video on TH-cam. The core of modern society!
The man who has the most toroids when he dies wins. Also, this was extremely educational. Thanks!
Ben - Thank you. This video was tuned perfectly not only to my existing grasp of electronics, but also the way that I learn. I can do math, but I don't think in math, and thus since electronics is only a hobby for me, magnetics have always remained a subject of blurry black magic where I don't know and can't understand one of these variables from another. I think I retained about 1/2 to 2/3 of the material here on the first pass, so, that's about 99% more than I ever have before. One of the biggest problems in education in my opinion is that usually the people who understand something the best, are the worst to teach it because they just intuitively got it. They don't know how to think like someone who doesn't just instantly get it. Or, people who learned something at a high level giving a simplified high-level explanation rather than an actual introductory explanation. So a lot of sciency fields end up dominated by people preaching to their choirs, using only the explanations that they understood themselves when they learned it, kind of like an unnecessary gatekeeping as if they insisted on teaching the class in latin. Don't already understand latin? Oh well, guess you don't get to learn calculus/magnetics/optics/etc either. There are very, very few people in the world who break down these barriers. I'd say this is probably the best laymen's explanation of magnetics available to the public, so, thank you for adding something unique to the world.
i learned more about magnets in the first 10 minutes of this video than i did in school growing up.
40 years in the trade & you just tied a few things together for me! Take a bow Ben. Thank you.
Awesome! This explained so much, by providing a more intuitive framework, and connecting it to what I already know about electric circuits. Thank you so much!
This is the video I've been waiting for. Nobody on the easily googled internet explains things like how magnetic flux is able to be "conducted"- this finally explains why you can lift a bunch of paperclips on end with a strong magnet, but can hardly affect one from the same distance away as the paperclip ladder was long.
Thanks
This is quite a pleasant and practical way to present the magnetic fields. Thanks you!
As someone who's done a couple of cumulative years of work designing novel magnetic materials, I have to say: this is an excellent video!
Thanks for the video, Ben! I'm super thankful for some of the newer magnetic scale systems that the chinese have developed which accomodate a greater range and resolution of values.
I now understand what the "permeability of empty space" refers to in physics charts. Thank you. This constant comes up all the time in my Wikipedia deep dives and I've never been able to make sense of it.
Wow, great video! I see your approach is a little bit different from what is typically used, at university we started with fundamentals and gradually came to materials and stuff, yours is very easy to understand nevertheless. Here's a few suggestions: when measuring BH curve with an oscilloscope and secondary winding, you could just use RC integrator instead of mathematical function, that would be simpler and I guess more availible to most of your viewers; also it would be very interesting to see a BH curve of a permanent magnet, as far as I understand it's almost rectangular for these kinds of materials.
I am preparing to start a job where we manufacture the large cables that're used in MRI machines. My understanding of basic engineering topics is sound, however due to my particular learning style (as well as personal need to review and revise my subject learning, even when I know it very well), I've been searching for some videos to help get me started.
I must commend you for your teaching style and organization. I can't tell you how many professors teach without context or relating it to practical uses (like how it'll apply to the real world), and even in basic discussions with my classmates, we don't really understand how to explain the why, but are adequate in performing the math.
Thanks near solely to this video, I've managed to get a great baseline on the topic of magnetism, and applying it to my job. A genuine thank you, as well as plea to future teachers: Use this teaching style as inspiration. There are many different ways to teach a topic, but regardless with how you feel about it, people are becoming far more visual learners who need direct applications, rather than baseless equations and dry math.
Thank you for the explanation. Great content.
This is one of the best magnetics introductions I've ever seen. It is so easy to get loose on math and be disconnected from the physics behind. When I learnt this on my second year of EE, I was able to solve exercises so I passed,, next year I was an teaching assistant, and then I started to understand. Finally truogh labs classes and a few years I got enough physical understanding. Today I think that some lab should be done in advance to the hard math/physics teaching so an integral is not a math challenge but a sum, a divergent is really a measure of something real diverting, and so on.
I did my big delve into transformer design half a decade ago and have learned since, but I'm still going into this excited. Have you read about the team that used superconductors to make legitimate "wires" for near lossless magnetic field transportation? It was still only lab work when I read about it. I hope more work has been done on that, it was very fascinating.
I thought that magnetic fields are the arch enemy of superconductors.
I can remember "glass iron" (extremly fast cooled iron), which had excellent magnetic proprieties for transformers...
it's true that superconductors have a critical flux density beyond which the superconducting state is destroyed and the magnet is quenched, but it is very high for the perovskite high-temperature superconductors like YBCO. This is why advanced YBCO tapes are being used in the next generation compact tokamak fusion reactors currently under construction like MIT's ARC design and Tokamak Energy's ST40 compact spherical tokamak. th-cam.com/video/NuiQTDanHx0/w-d-xo.html
Atlas WalkedAway -- Do you mean _transport_ like putting it in discrete shipping containers, for movement through space?
Probably the best video demonstrating the difference between Flux Intensity, Flux Density and Filed Flux.
I have to agree that this is a very good educational video. Just a few remarks.
When talking about the saturation you should mention that the curve does not turn horizontal up there but continues with the slope of the permeability of free space.
Your text notes are too small to be read on a screen.
@42min your small toroidal ferrite "transformer" is a filter coil meant to filter out high-frequency disturbances from a mains supply by passing phase an neutral through the two windings.
Also You Mention AMPS/ TURNS Ratio. that is WRONG. Reference, the NEWMAN MOTOR. or My motor . th-cam.com/video/vjxzKuikg5Y/w-d-xo.html
"amps times turns" is not wrong - that's physics!
www.phact.org/articles/free/newman.php
Sorry, its not a Rule. its a convenience. - and entirely dependent on the resistance of the wire. - EG. you can have unlimited turns, if you have superconductor wire. like iridium alloy. - oh and you can just use litz wire copper also
lol yes, newman was terrible at demonstrations. - he took the theory in the other direction with tiny wire, too choke the current. - 50,000 turns for 2 watts input, - -- ,it has too move something rite ? , even with huge magnets... this proves even our electrical intuition is better than "amps times turns" - that's physics!
I've studied engineering and physics. As such, I've covered this content in substantial detail and yet this short video was equally as useful in providing the INTUITION about magnetism as the countless hours of theoretical work I've done. Obviously for professional application of this technology, the theoretical knowledge is indispensable, but for the sheer joy of science, the INTUITION is all that is required.
Hi Ben! Great video. One question though... I thought that the residual magnetic field that remains after the external field is removed is called the magnetic remanence, not the coercivity. The coercivity is the strength of the external field necessary to cause the material to become magnetized, a measurement of "magnetic hardness". Once the material is magnetized and the external field is removed, the strength of the residual field depends on the remanence of the material. Did I misunderstand something? (I've only watched the video once so far...)
I think you are absolutely correct! In fact, it's been a long time since I've heard the word remanence, and since the two properties often go together, I forget they are in fact separate points on the BH curve. Thanks for pointing this out!
I was going to say that but luckily I searched for 'remanence' first :-)
Also, the energy it takes to drive the magnetisation per cycle is effectively the area of the BH curve, so that is a handy guide when testing junk-box coils.
50/60Hz current transformer construction is fun, I had to order special low coercivity toroids for a power-tool monitor that auto-triggered a shop-vac.
I find these tools handy - www.mag-inc.com/Design/Design-Tools
I like this part of Ben: when he muffs something (very easy to do on a subject like this), he admits it, and that's it. There's no shame in it. Stuff happens. Lord knows I have made a lot of errors in my professional life. All science and engineering practitioners should be like Ben.
I seem to recall _remanence_ also being called _retentivity,_ which seems a more descriptive term... though with 5 short syllables, it is a bit of a tongue-twister. At least retentivity will not be confused with _revenants!_ en.wikipedia.org/wiki/Revenant
@@PaulTurner_Haizo Please share schematics for that circuit!
May I propose the Best Science Teacher on You Tube awards? Give a couple to this guy! Thanks dude.
Who cares who came first? In my experience, that's not a good thing. I'm just happy to have another video from Applied Science.
At 48:17. The problem is..." You can't always get everything that you want. but, you can get what you need!" 😊 👍
I think that I have heard that before.
Thank you for a great video!
Wow, a lot of great information in that hour. Many thanks for putting that all together for us.
Watched this video again the 3rd time. I had some old copper ballasts that were being scraped in my apartment lighting (after 7 years of running) and being replaced with electronic ballasts. I collected them and planning to do some experiment. Your video comes very handy and practical.
The energy that's put into a permanent magnet at its time of manufacture, where does that energy go when you heat the magnet to its Curie point? Is it converted to heat then lost to space by radiation/conduction?
whoa good question
No energy is stored in permanent magnets, thats an illusion.
example:
Take a jar of pennies, reorder every pennies in the jar so the face point upward, this takes energy. Now, shake that jar, did the pennies get warmer bc they are now randomly oriented? No
Edit:
Permanent magnet are made out of "magnetic" atoms, the magnetization just align the atoms (cluster of) in one direction, this rotations heat up the magnet while it's manufactured.
Heating over its Curie point, just randomize the atoms back.
International Mutual Neutralist Party Templates
that's a great explanation actually
MrJimbo1qaz yes, if you try to put two of the same poles together you will feel the force pushing the poles away. If you keep the poles together you are putting in work to counter the magnetic force. Work is the transfer of energy and has the same units.
MrJimbo1qaz: It always require energy to get from a chaotic (randomized clusters) system to an ordered one.
This is possibly the best youtube tutorial I have ever watched. I wish this had been available all those years ago to watch before lecture 1 of my Uni Electromagnetics course!
This is amazing. I need more videos in this. I love electronics and this goes hand in hand.
RJ Anderson
This was one of the best explanations of the fundamentals. There are quite a few older videos that I've come across that demonstrate the subject of magnetics as they relate to transformers/electronics. I have saved everything I've come across over the last few years in playlists. Originally they were all private and simply intended as a form of personal reference. A few months ago I decided to make them all public along with my subscriptions list. (I'm not monetized, I have no intention of changing that, and I really don't care if anyone checks out what I've done. I have nothing to gain.) The reference is just intended as another FOS'y source for anyone that is interested.
I have a playlist called "Fundamentals Power Supply." About halfway down that playlist are a few videos from a CC called Eric Goodchild. IIRC he goes into this subject really well and built a saturation measurement device. Old videos like this are hard to find on YT as the SEO of YT is setup to heavily bias new and/or monetized content. I don't hold monetization against anyone IMO. It's their right as a CC and I respect that. However, there are a lot of channels from brilliant people who decide they do not want to monetize and do not upload regularly. Sometimes it can be difficult to find them.
Stay Curious ;)
-Jake
As someone coming from a Physics background my study of E&M (and magnetics in particular) was always centered around behavior in vacuum, with material considerations always rushed through without much depth or consideration. Seeing a systematic treatment of magnetic behavior in materials analagous to electric behavior in materials (electric circuits) has done a lot to remedy my aversion to "practical" electromagnetism in such a short time. Really well done.
That scope is amazing!
Would you be willing to do an updated lab tour?
Here comes the much-needed video. There is not enough content on Magnetics available on youtube, this video comes to fill that gap. I also liked that fact that it is a long video. I love detailed videos.
Wow, this video is long! Thank you for this. Your videos are awesome!
Excellent video. Not only the overall presentation but the multitude of little "tips and tricks " peppered throughout.
Here is a confession for you sir:
I am about to finish my Bsc in physics, I am Major in physics and minor in mathematics. I always viewed experimentalists as those whom their job is just the repetition of the same process (Do 1 2 3 take data then the next day do the same thing). I hated experiments in the University to be honest! Not that I actually hated them, I just thought what they are all the same thing, I would rather take a pen and a paper and solve equations rather than repeating the same thing everyday for the rest of my life.
Now, I think I know what is the problem. Experiments are not fun in doing them, they are fun in building and debugging them. They are like a programing code, you will have fun building and debugging a code "say a calculator", but you will probably not have fun using it to calculate things.
You inspired me sir, I am going to apply for theoretical and mathematical physics PhD next year!
Funny, your view of experiments is my view of theory (as it's commonly done in physics, computer science is somewhat different and more clear): why solve the same equations and the same (type of) proofs over and over again, yet learn nothing in any depth, if you look at it honestly.
I think the real difference is how much creativity and insights you gain during the process, while reducing the frustration factor involved with "tooling" issues. The tools in theoretic problems, are mastering the theoretical concepts and math that are usually pretty remote from the topic itself and often have quirky formulations.
Uh okay. I love theory because I don't solve the same problems over and over again! I don't like any course in my program LOL. I love the subjects but not the exams nor the ways of teaching. (I research what I like in the subject, and a lot of the time I learn it by myself from various sources)
So, I think we hate theories and experiments because of the methodology of teaching.
Just to tell you how I fell in love with theory:
1- Find a research project of interest. Something you really don't mind investing a year in reading and studying.
2- Find good and multiple sources.
3- Ask and discuss others.
I've already watched this video a few times since you released it. But man this is so information dense, I could watch it dozens of times and still keep learning stuff. It's like the educational version of something like The Simpsons is with humour. It's so densely packed that you find new things every time you watch it. Or just old things you forgot about.
You can't always get everything that you want, but you can get what you need.
LOL.
Thus quoth the Rolling Stone.
@@YodaWhat In their famous song about low frequency transformers.
@@gatyair82 Well, not specifically, but the lyrics seem fit to generalize rather widely.
Can't help but be reminded of Dr. House
It’s definitely taught heavy on the math. Spent the whole semester deriving equations and didn’t remember much. It wasn’t until presentations like this came along that it all clicked. There was definitely value in deriving those equations, it just took a 15 years to put it all together. Thank you.
There's a channel by a guy named Jeff Quigley I think it's spelled...he posts a lot of old BandW videos about electronics and magnetics that are 1950's Navy productions...pretty interesting.
This is incredible. I did fall asleep a couple of times but that's me.. I used to miss half the lessons back in Engineering school. But with TH-cam I wake back up and go back. Thanks for such hard work to tech us so much !! Your channel is amazing.
8:30 - You can see the compass twitch as Ben waves the magnet about :P
It's a pretty scary magnet. I'm glad that I haven't been pinched by that one!
Applied Science The wooden wedge-based handling techniques that brainiac75(?) has developed for the contact and separation of big magnets are really interesting and effective.
I've had a love affair with magnets and magnetism for somewhere in the neighborhood 50 years, read a lot about magnets and this video does a good job of summing it up. Great job one of your best video yet. Thanks
If you have wire wound around an iron core, and at a given current it is saturated, if you pass a higher current through the wire, what happens to that extra magnetic field or flux that is being generated?
Good question. Once saturated, any additional H caused by additional current in the coil will behave as if the iron didn't exist at all. It will spread out through the air just as it would without the iron. It would be nice if the transition through saturation were like a brick wall -- snapping into a new regime suddenly. If this were the case, we could first measure the field caused by 100% saturation, then measure the field caused by air (with the iron core removed), and then sum them together. In the real world, the transition to saturation is gradual, and the field making its way outside the core will interact with the partially saturated core, and cause things to become a little more messy.
The phenomenon you are looking for is called magnetic flux leakage. The magnetic field will literally leak out of the iron core and start flowing through the air around the core instead.
Magnetically, it would make the field weaker but would make very little difference overall. Your essentially shorting out a small section of the magnetic field. Remember that flowing electrons create a circular magnetic field that flows around the current flow. So the magnetic properties of the wire aren't very significant, it's whats around the wire that has the most impact. Electrically on the other hand, by using wire with a higher resistivity, you've increased the resistance of the coil. Which means you need more voltage to have same amount of current flowing through the coil. This means you will need to have more input power to produce the same magneto-motive force and your overall efficiency would drop.
@Mai Mariarti The iron wire will get hot.
I have had this on my watch list for six months or more, because i knew it was going to be a ton of information to absorb, and I needed to be ready. Wow, it was excellent, and I'm glad I didn't give up!
I want to rewatch it after my brain cools down.
The green thing u shown in the beginning through which we can see magnetic field lines of magnetic.
Please tell the name of that thing. And from where can we purchase it?
Ah that's magnetic viewing film, pretty cheap to get online.
www.amazon.com/s?url=search-alias%3Daps&field-keywords=magnetic+viewing+film
"Magnetic Film" from ebay, aliexpress, etc. Cheap and fun!
Asad Mirza thanks
Jonathan deWerd thanks
Stuff like that is overpriced on amazon. I'd suggest aliexpress.
A well explained and easy to understand breakdown of the working principles, definitions, units, terms, plus other aspects which make up this complex subject, that even after 35 years as an electronics technician I still have trouble with. Thanks so much for sharing. 😉👌🏻
it's embarrassing that my college professors did a worse job explaining a concept in 3 years than you just did in less than an hour.
this is what electrical machine classes should look like before the lectures go through all the theory behind it and hard to solve maxwell equations , this give u better idea of this principle and make you understand all the maths and theory . nice presentation
I take it you like The Rolling Stones! ;)
I came here looking for this comment!
This changed my life. Thank you for working through the terms of dielectricity in such a tangible way!
Frigging magnets! Am I right or am I right?
You are such a good teach my man. An amazing balance between almost kindergarten "hands on experiments", human intuition and college level theory.
I feel like anyone who didn't follow everything, could easily google the tiny missing bit, then come back and be good to go.
If you put a highly diamagnetic material in place of the air gap, would you get a net negative reluctance? And what would that do to the magnetic field flowing in the "circuit"?
I was wrong about this in the video. One of the other commenters helpfully pointed out that diamagnetic materials do not have negative permeability, but rather a permeability that is lower than empty space. This means that in an H field, the material will conduct magnetic flux more poorly than empty space itself). The magnetic field lines will partially flow around the diamagnetic material instead of through it because the material poses slightly more reluctance than the space around it. A compass needle aligns itself with the magnetic field, while a piece of diamagnetic material will become perpendicular to the field lines.
more please. can't get enough, you explained this so well. This is better than the majority of university courses because this actually makes sense.