Electricity, Magnetism and Special Relativity (corrected)
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- เผยแพร่เมื่อ 19 พ.ค. 2023
- A magnetic field is an electric field perceived from a different relativistic frame of reference.
This video is a corrected version of the previous video by the same name.
Really a great explanation professor my views releted with this electrodynamic just changed im very lucky to find this video out our explanation was fundamental and so easy for people like me with beginning know thanks a lot sir. To share the concept in such a easy way
How does this only have 578 views??
Honestly a great video. Good and easy explanation and visualisation of the subject. Thanks a lot.
The best explanation ever. thank you very much
Very well explained
Thanks, this is the way I was taught and until we invent a monitoring device to actually see atomic structure (protons, neutrons and electrons) and subatomic particles. We will only see the effects of this phenomenon. Like the white light we see with our eyes. We know its there but we still can't see the photons or packets of electromagnetic energy.
"Adam you failed electromagnetism 101."
I'm sorry peasant I was busy with magnetomagnetism and electroelectricity
Bob - How may obtain a list of your textbooks for a course I am teaching? The course is on DC and AC electric power and the physics of materials in support of the former. Thank you
I know all this. I would love to see the math to show why permittivity is so much worse than permeability.
Great explanation. Thank you!
But how does this model explain energy losses when emitting EM radiation? Why one have to make work when feeding an antenna? Why accelerated charge loses its energy in this model?
That stuff about negative and positive charges flowing in opposite directions and cancelling each other out makes no sense. If you want to treat the current as positive "holes" going the other way, you have to treat the electrons as stationary. Otherwise you have twice the current.
Agree. I have studied this in my Physics BSc and I found the explanations a little hand-wavy. It feels as if there's a gap in our knowledge and it's not being addressed. Stuff not sexy enough for new researchers to re-xplore it
This is okay because "holes" don't really have charge. If we treat them as having charge +1, then we need to be consistent and shift all charges by +1. As such, the charge of the electron is neutral and doesn't produce a current while moving.
This made no sense to me at all. Positive charges don’t move, electrons do. Holes are totally unnecessary
no discussion about that every electron is a tiny magnet due to its orbit, spin & direction. That only unpaired electrons (think valence) can create magnetic fields. The paired electrons cancel each other out because the spins are in opposite directions.
Nice video and presentation.
Let see if we understand each other.
1. Electrons and ions moves through electrolytes and vacuum but metal.
2. Electric charge moves on the boundary of metal that electrons and ions cannot.
3. Charged electrons and ions moves through vacuum enables charges to migrate through vacuum, and hence electric current. The current in a cathode ray tube.
if you counted the charges, you would not witness *more* electrons. It did not create matter to move.
I'd say magnetic forces and electric forces are just different manifestations of the electromagnetic force, which is a fundamental force, unlike either electric or magnetic forces.
Why would you say that as opposed to saying that magnetism is a name for electric forces?
I thought the field was a more screwy form in the direction of electron flow
If there was a positive current going one way and equivalent amount of negative charge going the other way, each is supposed to create the same magnetic field but in opposite signs and therefore no magnetic field should be present. This idea of positive holes moving is just contradictory and seems like hand-waving.
Where are these magical moving positive charges coming from? If the protons are the cause of the positive charge and the protons aren't physically moving (that is the whole point of metals isn't it? A free electron that can move around but not protons ( or kernel) drifting around? - except through physical or thermal additions of course.), then what is causing the positive charges to move?
I'm fine with length contraction on the negative charges moving because the electrons are moving. But once you start moving the positive charges too, they too will experience length contraction and that would cancel out any effects from "more of one kind of charge per inch" since the moving electrons also have more charges per inch and you are right back to no charge at all.
Do we actually need the positive charges to move at all to explain where the charge imbalance is coming from? Doesn't this muddle the whole explanation?
Very nice video like to listen hour together.thanks
doesn't explain why there is a magnetic field associated with even a single electron/proton moving at a constant speed, and the also the drift velocity of electrons is very small about 1mm per second, what relativistic effects such a small velocity will have, this relativity based explanation seems hand wavy at best.
This is all based on Purcell (1963).
Purcell uses STR to explain the magnetic field near a wire. He applies LC to the train of electrons drifting along the wire, & he calculates that the increased charge explains the extra force on a test charge moving near the wire - no magnetic force needed.
What a load of krapp.
1. Purcell starts off by saying that a stationary charge near a wire with zero electricity suffers zero force (true).
2. And that when a current is sent along the wire the charge suffers zero force (true).
3. And that when the charge is then moved along next to the wire the charge suffers a force (true).
4. Re (2), Purcell says that the drifting electrons decrease their spacings as seen by the charge due to LC, which would increase the charge on or in the wire.
5. Re (4), Purcell says that we know that in (2)&(4) there is no increase in charge on or in the wire - hence the drifting electrons must somehow increase their spacings to offset the LC.
6. Re (3), Purcell uses LC to calc the denser spacing of protons, to calc the force in (3).
7. And then Purcell uses (5) to in effect double the calculated force in (6), to make his equation work proper.
And Veritasium & Co on youtube reckon that the sun shines out of Purcell's bum.
Protestants and Catholics fighting again? Most people don't even understand Transmission lines, little alone Maxwell-Heaviside equations. You are arguing to the 0.01% of those that can understand.
It's also obvious that the teacher has the mindset of teaching young people, as he always talks about 'conventional current' and that the current is the energy in the wires, which I have learned from you know who (he must not be named) Veri.... Rick Hartley ( that was close) that isn't how Electricity works. Our case and point of the Transmission Line, which Electrons don't travel down the wire at all, they just isolate No current (Electrons flowing) form the Power Station makes it to my house or to his house
@@Dazza_Doo
ELEKTONS & ELEKTICITY & ELEKTRONS FOR BEGINNERS.
1. A good conductor of elekticity can be called a metal.
2. A metal is a good conductor of elekticity.
3. A metal has a thin layer of elektons on its outside surface - that is what makes it a metal.
4. Non-metals do not have a layer of elektons on their surfaces.
5. Elektons are photons that hug the surface….
6. Whilst propagating at the speed of light in the medium touching the surface (eg air)(eg plastic insulation).
7. Elektons move in every direction on the surface of a say Cu wire - but (eventually) mainly along.
8. The propagation speed of elektons duznt depend on the kind of metal - all kinds of metals give the same speed.
9. The ruffness of the surface slows the speed of elektons - due to the extra distance up&down over the ruffness.
10. Elektons have a negative charge, equal to the charge attributed to the (silly) standard electron.
11. Elektons go straight ahead - except that their trajekt is affected by other elektons (due to repulsion).
12. Hence, after a while, elektons tend to move mainly along a wire (albeit in both directions).
13. And, elektons follow the surface.
14. If the surface of a wire duz a u-turn (eg at the blunt end of a wire) then elektons do a u-turn at the end (koz the surface duz a u-turn)(ie elektons follow the surface).
15. Elektons form a thin negatively charged outer surface layer due to repulsion from atomic elektrons.
16. Atomic elektrons are photons that orbit (hug) an atomic nucleus.
17. The outer orbital elektrons escape from the nucleus, & form an outer layer of elektons (now hugging the general surface rather than hugging individual nuclei).
18. The elektons are attracted to the positively charged nuclei.
19. Different metals will have a different degree of saturation of elektons.
20. The better conductors will have a denser saturation of elektons.
21. A battery can supply elektons at the positive terminal….
22. And rob elektons at the negative terminal.
23. The supply etc of elektons can result in what we call voltage, or potential.
24. The supply etc of elektons can result in what we call charge.
25. A dead-end length of wire touching a positive terminal will be saturated with elektons going both ways along the wire (doing u-turns at the dead-end).
26. Elektons do not reflekt off or at a dead-end (they do a u-turn).
27. When the flow of elektons going each way is equal then their magnetic fields cancel…
28. And hence their nett magnetic field is zero (in the far field)….
29. And there is no heat loss in the wire.
30. A dead-end length of wire touching a negative terminal will be saturated with elektons going both ways along the wire (doing u-turns at the dead-end).
31. The numbers of elektons going up & down a dead-end wire will depend on the degree of saturation.
32a. The degree of saturation will depend on the surface area available etc….
32b. And whether the wire has a coating of insulation.
33. This saturation creates what we call resistance….
34. Or, if u like, this resistance creates saturation (many processes are chicken'&'egg).
35. Once u have learnt the above rules then u will understand that if u somehow discharge/short/earth a length (L) of wire, then u can expect that the primary discharge will take a duration of 2L/c seconds (ie it wont take L/c seconds).
36. And the discharge voltage will be V/2 (ie it wont be the more obvious V/1)
37. And if that there wire is insulated then the duration will take 3L/c seconds (as per (6) & (32b)).
Enuff for today.
@@atheistaetherist2747 that's a lot ... Most of the top part seems to be Skin Effect.
Then you talk about Batteries creating the flow of electrons from the Positive end of the Battery, it's not that important, as Current can flow in both directions and do with AC. So Electrons flow isn't important, as the EM field is the energy in a circuit. It's only important for Diodes and 1 way devices with are Doped Silcon, as you know. There is no heat loss in a wire, I assume you mean that the conductor doesn't radiate IR waves? Sure they do, everything Does, that's the property of matter. Lets try this - can I use a IR camera to see circuit board traces? Yes of course, in fact they use it to detect hotspots.
How old is this text book? The old use of the term Electrons is interesting.
Electric Current is the Effect of the EM field on the conductor. Electron Drift is Microscope - this is proven by AC circuits were NO Electrons (Current) will travel from the AC power source to the end load (See Transmission lines). Therefore, current direction matters not in regard to the flow of Energy in a Circuit, only for components that have been Doped in such manner. Current and Voltage are measurements of the Medium, they are Effectors not Affecters.
Twice the speed? How is that? Wouldn't that mean twice the current?
Wait seeing this explaination i feel like electrons and protons etc are living things like they have conscious😂
Why does magnetism follow iron but not cobber? Iron and cobber are both metals and relatively good connectors. What I am saying is that there are materials that stop magnetic fields but not electric fields and visa versa. Both electric and magnetic fields exists I believe.
AFAIK, there is not material that can 'stop' or block a magnetic field. There are no magnetic charges. (See Guass's Law for Magnetism) Magnetic materials can only redirect the magnetic field, so as to reduce it outside the material. IMO, electric and magnetic fields are only manifestations of the fundamental force; the electromagnetic force.
Special relativity has nothing to do with it. The electrons are moving well below the speed of light as they actually travel a short distance from atom to atom. The lorentz contraction is negligible and would not explain the kind of force we see. In deed, Maxwell Equations and in particular Farday's law was well established LONG before SR. It is simply that moving charge causes magnetic field.
Here do this "thought experiment." Imagine an electron moving all by itself in free space. There is no charge imbalance of another proton. As it moves by a compass, it will cause the needle to bend. There is no length contraction or some kind of positive/negative charge imbalance. The electron motion, all by itself, is enough to cause a magnetic field. And the same thing is happening in the wire.
This claim is as silly as a claim that electric fields arise due to mass and thus gravity resulting from SR. And the argument against this bit of foolishness is the same as the one above.
Please just remove the pen caps and leave them off the pens. It is so annoying putting them on and off!!!
I suppose you are not aware that if the markers are kept open for some time, they dry up. That's why he is putting the caps back on after writing. He is making such a great effort to explain the subject, the pen shouldn't have distracted you.
Consider an electron outside a current carrying wire and not moving relative to the wire. So due to length contraction of the electrons in the wire, the electron outside the wire ought to be repelled but we know it isn't ------> utter nonsense.
A current carrying wire represents zillions of changing electric fields due to relative motion between electrons and positively charged nuclei. Changing electric fields -------> magnetic fields.
End of story! Nothing to do with failed relativity whatsoever!
A current-carrying wire creates a magnetic field. While it's tempting to think a stationary charge near this wire would feel a force, that's not true due to relativity. See the moving electrons in the wire undergo length contraction, appearing more dense but the "holes" left behind by these electrons also move and contract, appearing more dense to. So those two effects cancel out, and relativity perfectly explains why a resting charge nearby feels no net force due to the wire's constant magnetic field.
@@pedrooctavio6383 Sorry, but that just doesn't work.
Not only is this situation a typical failed attempt to apply relativity to everything, it is in fact just another proof that relativity is wrong.
@@hosh1313 Hey, I'm ready to believe you if you can show a mathematical proof... or just one example of an experiment that proves Special Relativity is wrong. (So far 100 years of questioning Special Relativity hasn't managed to do that.)
@@willthecat163 Here's a few things for you to consider.
1/ Cosmological red shift is a violation of the conservation of energy.
2/ How does a no aether theory explain an accelerating expanding universe? Where does the force come from?
3/ Aether can explain unaccounted for gravity in the outlying regions of galaxies.
Aether theories have no problems with these issues.
Dude I have a question. How does an electromagnet work? How does it attract stuff? Why does a moving charge exhibits magnetic field?
I see all the explanations using Einstein's relativity is in context of moving charge. But when we make electromagnet we don't have to move iron in order for it to stick. It stick right away. But why?
Dumb explanation, for electrons and protons psychology does not works.
That is completely wrong.
Why?
Omg!🥲🙌, finally! I've found my answer!