What is a Magnetic Field? (Electromagnetism - Physics)

If you have studied or are studying physics, or even if you are just a physics fan, you must have already met magnetic fields, and more than once!
These show up a little everywhere: of course in electrical sciences, but also in planetology, astrophysics, medical physics, analytical chemistry, and many other subjects. At school and in Uni, you have been taught how to manipulate them mathematically, and how they are an intricately involved in today's technology (motors, generators, transformers etc…).
But do you actually know what they truly are physically? For example, could you explain it to a young student that encounters magnetic fields for the first time in physics class ?
That is the exercise I attempted with this video
First, we review what you learned in high school, starting with a simplified version of Ampere’s law: an electrical current generates a magnetic field that curls around it. We also discuss how a magnetic field affects the path of a moving charge.
In a second section, we take a brief turn in order to observe one of the consequences of Einstein theory of special relativity: Length contraction.
The third section puts everything together and draws a coherent picture of the nature of a magnetic field. And in a conclusion, we realise that a magnetic field emerges from the combination of electrical theories and special relativity.
And of course all is spiced up with reflections on how historically, magnetic fields took such a predominant place in modern science.
I hope you enjoy this video, I sure had fun producing it!
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Structure of the video:
00:00 Introduction
00 :34 30K subs!
00:55 Content of the Video
01:32 Magnetic Effects - description of a charge moving parallel to a current carrying cable.
02:38 Magnetic Effects - magnetic field generated by an electrical current
03:09 Magnetic Effects - Magnetic force on a moving charge
04:14 The birth of electromagnetism, a historical reflections about magnetic fields
05:27 Length contraction
07:05 The nature of magnetic fields
09:55 What is a magnetic field ?
10:17 Magnetism is an emergent phenomena (a discussion)
11:41 End of video salutation to the Physics Made Easy community
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Prior knowledge required:
In order to fully grasp the content of this video, the viewer needs to be familiar with the following concepts already presented in a PME video.
_ What is a charge : • What is Electric Charg...
_ What is a field : • Electrostatic Physics,...
_What is an electric field : • What is an Electric Fi...
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Addendum: regarding conservation of charge…
You might wonder : because relativity changes the charge density experienced by a moving charge, could this violate the principle of conservation of charge ?
No, it doesn’t. The reason is that for a current to flow in a circuit, the circuit needs to be closed, i.e. in a loop: relatively to the motion of the moving charge, the current needs to flow in the opposite direction in another section of the circuit :
Imagine a moving charge q magnetically affected by a current going from left to right in section A of the circuit. The charge will also see a current flowing from right to left in another section of the circuit (let’s call it section B).
For charge q, section B will have charged densities reversed compared to section A. On the other hand, it might not be magnetically affected that much, because that effect depends on spacial distance (inversely proportional). Overall, charge is conserved wether the observer is moving or not.
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Credits :
The script, the illustrations, the music and the video were produced and presented by Edouard Reny, Ph.D. in solid state chemistry and private tutor in Physical Sciences.
The galactic background at the end of the video : Traverse galaxy by F. Summers, G. Bacon (STScI). This background is more than an artistic view, it is a simulation : C Hummels, P. Hopkins (CalTech) and A. Wetzel (UC Davis)
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Need help with your high school physics ?:
Edouard provides one-on-one private tuition in Physics (face to face or by Skype). If you wish to know more about this, or contact Edouard, visit his website: www.physics-tutor.nl/
or this one (for French speakers): profdephysique.fr/

[@unnikrishnanms3431]

Simple...Lucid...Mind blowing explanation

[@PhysicsMadeEasy]

Thank you so much for your encouraging words!

[@photon434]

Complex concepts visualized. Magnetism is emergent -- so cool.

[@PhysicsMadeEasy]

Thank you for your kind comment! Yes Emergence is quite a common phenomena in physics (and quite fascinating must I say!). Other examples that come to mind immediately are temperature and mass.

[@combomaster99]

Something that keeps me thinking is how do magnets work in a vacuum. As there is some sort of static field emerging from a permanent magnet that does not consume any kind of power, does not need any kind matter to transfer energy from one pole to the other. Extreme strong magnets have large fields but are not detectable by any sort of visual camera yet are very much present. So much so that one could crush your hand if you held it between the magnet and a piece of iron or another magnet. This means its having a clear and strong effect radiating onto the fabric of space. But what exactly is that field made off. The only way you can know its there is by having something that interacts with it. As far as i understand your explanation of those fields are 'Electrical Phenomena'. Awesome video, sorry if i didn't fully understand it. I appreciate it immensely that you take the time and effort explaining such topics.

[@PhysicsMadeEasy]

Hi Combomaster, most of the answers are in the video, and your questions, which are good ones, show that you seem to have some misunderstanding about the concept of fields. You mention energy (power) not being consumed by a magnet or field. Yes. You can see a magnet like a mountain and a map of the height as the field itself. Place a ball on the mountains slope, it falls down the slope and gains velocity (Kinetic energy). The energy doesn’t come from the magnet or the field (the mountain or the height), but from the person that went up the mountain to put the ball there in the first place and gave that ball potential energy … Maybe check the video ‘what is a field?’, and then ‘what is an electric field?’. That could help. A field is not an object, so cannot be directly observed as such (like with a camera), only its effects on what is positioned in the field. Some actually think that fields are just an abstract mathematical tool useful to model the world around us (I am among them, but only as far as classical physics is concerned). You had good questions, well-constructed, that show Curiosity. Continue digging!

[@spencerwenzel7381]

I have wondered this for a while. Why does it matter that the positive charge, q+, moves relative to the positive charges in the wire? For example, if we were to keep q+ stationary with respect to the wire, the electrons would still move relative to q+ and therefore length contraction should still occur. In your example with the bicycle and the table, there were only two objects, you and the table. Why not with just the two objects, q+ and the electrons in the wire?

[@PhysicsMadeEasy]

Hello Spencer, Very good comment. While I was working on the script of the video, I asked myself a similar question : If the wire with no electron flow is neutral for a moving test charge, how come it is still neutral when a current is flowing. It is true that what I say in the video suggests otherwise. It didn’t stop me from posting because all other lectures and videos I saw on the topic didn’t seem to consider this question. Even Feynman, in his famous lectures, presents a special case, and just evades the question. I even asked chat gpt4, and it kept answering me in circle, haha ! I’ve been thinking about it, and I realised that the issue is that charge q+ is going much faster than the electrons : The emergence of magnetic effects become significant only for relativistic speeds of the test charge q+. Imagine you accelerate a proton (the test charge) in vacuum with a simple 9V battery. I calculated that the speed for a proton would be in the tens of thousands of m/s (roughly 42 km/s), and for an electron in the millions (roughly 1800 km/s). While the drift velocity of electrons in the wire electrons is tiny (a few mm per second). What actually counts is the difference of velocities perceived by the test charge between positive charges and negative charges in the cable. The effect of this tiny difference (= drift velocity) at small non-relativistic velocities is insignificant, but has a significant effect when the speed of the test charge becomes relativistic : At relativistic speeds, If you change the speed of the particle, that change will lead to a difference of length contraction for positive and negative charges that is significant. At low speeds, If you change the speed of the particle, that change will lead to a difference of length contraction for positive and negative charges that is so insignificant, that the cable can be considered as remaining neutral. The example on the video is more of a thought experiment, reality as it is, would have been very difficult to represent accurately in an animation… I should have discussed this in the video, but I believe this would have provided more confusion than clarity… (my videos are intended to provide the viewer with a first step towards a knowledge that they can then develop by themselves…). Best,

[@spencerwenzel7381]

@@PhysicsMadeEasy thank-you for the very detailed response. I haven't found a good explanation of this for years until your comment. It makes perfect sense now. Your ability to describe concepts clearly has been extremely useful to me in conveying similar concepts to my students. Really appreciate the work you put into making these 👍

[@cristig243]

​When you know it doesn't make physical sense, but you are still pushing it because of...einstein 👌​@@PhysicsMadeEasy

[@zBrush01]

Well explained to understand for a non Physicist as well. Thx 🖖

[@PhysicsMadeEasy]

That is a super comment, thanks! If in addition to help young students interested in physics, I can bring some understanding to non physicist, I just surpassed my objective!

[@vorsybl]

Thanks for making another video! Many of the previous ones have helped me understand physics better (especially the ones on waves, which were very confusing for me at first....energy, and work).

[@PhysicsMadeEasy]

Thank you for kind your feedback vorsybl. I am glad my work brings you closer to understanding physics :-)

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@jakirshah1683]

You are awesome in putting complicated things in simplified way. Students may benefitted more as well others . Please keep it up

[@PhysicsMadeEasy]

Thank you Jakir. I do indeed try to Make Physics Easy :-)

[@vaishakpraveen7093]

Sir i am from India and, Im poor in physics after watching your lectures i am understanding somehow Thankyou can you do gravitation videos

[@PhysicsMadeEasy]

Hi, I do not have many gravitation videos on the channel (Just 'why is gravitational energy always negative'). But I have produced a few years ago a full course on Gravity basics (where I start from the beginning). Check it out: www.udemy.com/course/gravity-the-basics/. It could help.

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@profelu1919]

Coming again to really study your content taking notes. You rock!

[@PhysicsMadeEasy]

Hi Profelu, thank you very much for your feedback. I am glad I have such a fan regarding my electricity and magnetism videos ❤️

[@funmylolarojo2589]

I have learned a lot from this. Thank you!

[@cala416]

really good and intuitive explanation, thanks a lot.

[@PhysicsMadeEasy]

You are very much welcome Cala.

[@daddyfrhuh]

Hello , professor glad you are still making videos for the community , your videos are so helpful that I cannot explain in words , Id just like to say please keep making physics easy and we will hit a milestone for sure ! Much loving and blessings ❤

[@PhysicsMadeEasy]

Thank you for your encouragements!

[@fysics_nerd0.0073]

I have a question, when we have the same speed as the cable, when we are "standing still", the protons will not move, but if there is current in the cable as in this example the electrons will move, why does that not cause the electrons to undergo length contraction, which would then lead to a proton beside the wire to be attracted?

[@julienprince1]

Great one, such a helpful video

[@PhysicsMadeEasy]

Thank you Julien

[@yuhannizar2857]

Good explanation, Thank you Sir

[@PhysicsMadeEasy]

You are welcome Yuhan

[@user-sz5dt9ih7f]

Wonderful again!!! Thank you, sir!!!

[@PhysicsMadeEasy]

You are warmly welcome!

[@dalenassar9152]

This video brings to mind something that has had me puzzled from the start: "THAT 12 YEAR-LONG GAP BETWEEN THE DISCOVERY THAT CURRENT PRODUCES MAGNETIC FIELDS, UNTIL THE DISCOVERY THAT MAGNETIC FIELDS CAN PRODUCE CURRENTS" When the 1st discovery was announced, then, INSTANTLY, (as a Cal-Tech physicist put it), "all scientists immediately ran to their labs to prove the the reverse was also true. i.e. 'current can be made to flow by a mag. field'. Then 12 YEARS went by with no success!!. How can this be?? It should have the same day! They set up B-fields and their conducting wires connected to galvanometers and started working tirelessly, putting wires in B-fields while watching the current sensors. Although MOTION of the wire was required, there had to be moments where they moved the wires into the field....even if they placed the wires into the field space BEFORE turning on the current, the detector would have jumped. These work tables were 'covered' with all kinds of current sources, switches, coils, detectors, etc. Your thoughts?? Thanks for the great ..as usual..video! --dALE PS, one other thing: I have seen all the physics of forces on charges moving in B-fields...mostly charged particles and current-carrying wires...But I have been looking for details the physics of an energetic spark in a B-field. IOW: how the charges and currents in a spark channel differ compared to a current-carrying wire. I would wonder how the F=BIL equation would be written for a free arc. Your unique videos are VERY valuable, and probably inspire much further than realized--very unusual!!

[@andersemanuel]

This was your best! Thank you.

[@PhysicsMadeEasy]

Thank you Manuel :-)

[@MR.LOCAL-X2]

Sir please post on electromagnetic induction and how it works

[@PhysicsMadeEasy]

Hi, we are getting there... As you might have noted, I am in a 'Electromagnetic mood' these days. The plan is to produce a few more videos: Magnetic monopoles, Faraday's and Lenz Law, and then I will conclude with a firework discussing EM induction in circuits... That's the plan, I hope time will allow me to do so! Up to now it has, so fingers crossed!

[@MR.LOCAL-X2]

@@PhysicsMadeEasy thankyou sir

[@castrothg]

Amazing content thanks a lot for sharing it.

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@sunitasultan7456]

Keep making videos. You teach really good, sir.

[@PhysicsMadeEasy]

Thank you for your kind words Sunita!

[@fridmamedov270]

3BLUE1BROWN, Dr. Trefor Bazett, You, are just amazing. Understanding is more important than the computation!

[@mdnurainansari3414]

Hy!! Thanks for this video... I can now learn deeply about this Thanks again

[@PhysicsMadeEasy]

You are welcome. mdnurainansari. I hope you enjoy it!

[@EduardOganesian]

OK, what about a charge moving perpendicularly to a current wire? The charge will experience a force sideways, can this be predicted by Special Relativity as well?

[@ConciousControl]

Hi, can you explain how a parallel pair of current carrying wires can have a magnetic attractive force between them? When the currents are both equal and moving in the same direction there is no relative difference in any of the motions of the charges in the two wires. Thanks.

[@PhysicsMadeEasy]

Hello, Let’s consider your example and name wires A and B. The currents in the wires are parallel and in the same direction (let’s imagine downwards). What are the electrons in wire A « seeing » while they move ? From they perspective, they see the electrons in wire B at rest. No length contraciton there. But they also see the positively charged metallic ions moving upwards… Positive charges will appear to get denser, and wire B will appear positive, so the electrons moving in wire A will be attracted by wire B. Repeat this reasoning for the electrons moving in wire B, and you’ll see that these are attracted to Wire A… Of course this is a simplified view, within each cable things are a little more complex than this, but you get the general idea… I hope this clarifies things!

[@ConciousControl]

@@PhysicsMadeEasy Thanks yes it does, but won't where also be a repulsive force acting between the two wires due to the moving positive changes?

[@hopcfizl3671]

Is there an explanation for why current is opposite of moving charge or is it just and agreement? And won't there still be electrical force on the charge from the current going through wire even when it's not moving? I don't see how the wire with current could be neutral.

[@PhysicsMadeEasy]

Hi, Yes, it is an 'agreement', as suggested by the name 'conventional' current. If you take a piece of metal (like a piece of wire), the number of electrons is the same as the number of protons, thus the charge density is zero. That doesn't change for the observer at rest if the electrons are moving uniformly in the wire. Finally, because the cable is electrically neutral, it will not generate a net electric field at the level of an external test charge at rest, so there will be no electric force on the latter.

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@marcseghatol6583]

Great

[@aminnima6145]

Love it, thank you

[@PhysicsMadeEasy]

You are warmly welcome :-)

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@Paulfly]

Nice explanation! I don’t quite understand why the “d” between electrons is larger than the nominal “d0”, could you please explain more about it? Thank you professor.

[@PhysicsMadeEasy]

Hello Paul. because in the example, the observer is moving along with the electrons, so their relative velocity (= difference of velocities between electrons and observer) is less than at rest, thus the distance between electrons seen from the observer increases.

[@Paulfly]

Thank you professor. Given the test Q is static. Assuming no current flow thru the cable, the nominal distance between electrons is same as protons, which is d0. When the cable moves upward with V1 relative to test Q, from the test Q’ view, distance between electrons and protons becomes d1. When applied voltage, the electrons move downward with V2 which is relative to the protons. if V2 is equal to 2 times of v1, then relative to the test Q, electrons is moving downward with V1 relative to the test Q. Thus the distance between electrons to the test Q will be still d1. Am I correct…

[@PhysicsMadeEasy]

@@Paulfly Hello Paul, Yes you are correct, if V2=-2V1, the length contraction for both protons and electrons would be the same, thus, positive and negative charge densities in perspective of charge q+ should be the same, so no net force. But in my video there is a little imprecision… (which occurs in all lectures I have seen up to now about that, even Feynman’s !): The effect becomes significant at relativistic speeds for the charge q+. So the situation you propose would not really happen. Imagine you accelerate a proton (the test charge) in vacuum with a simple 9V battery. I calculated that the speed for a proton would be in the tens of thousands of m/s (roughly 42 km/s), and for an electron in the millions (roughly 1800 km/s). While the drift velocity of electrons in the wire electrons is tiny (a few mm per second). What actually counts is the difference of perceived velocities between positive charges and negative charges in the cable. This tiny difference at small (non-relativistic) velocities is insignificant, but has a significant effect when the speed of the test charge becomes relativistic (look at the structure of the length contraction formula). The example on the video is more of a thought experiment, reality as it is, would have been very difficult to represent accurately in an animation… I should have discussed this in the video, but I believe this would have provided more confusion than clarity… (my videos are intended to provide the viewer with a first step towards a knowledge that they can then develop by themselves…). Oh, by the way, your comment was excellent. Well done ! Be well

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@TOKAYASSHOP-hl2gw]

Hi I thought length contraction happens when moving in the same direction than motion observed not opposite direction.. can you help me here? Thanks

[@PhysicsMadeEasy]

Hi, Length contraction occurs when there is a difference between the velocity of the observer and of what is observed. The direction doesn't matter (as expressed by the square on the v in the length contraction formula). If an observer, moves in the opposite direction than the observed object, the speed difference between the two increases, thus length contraction becomes even more pronounced.

[@TOKAYASSHOP-hl2gw]

@@PhysicsMadeEasy i think I’m missing something, doesn’t Lorentz say that length contraction happens in the direction of movement?

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@marciliopc]

to use Lorentz contraction the charge velocity must be in the order of the light velocity. The electron velocity in a cable is too small (cm per second). So how do you justify this use?

[@PhysicsMadeEasy]

Yes but a charge moving next to the cable will have a velocity being a significant fraction of c. At these velocities of the moving charge, the differential between positive and negative charges velocities in the cable, which is small in absolute, should become significant in the perspective of that moving charge.

[@turkishwithemre]

The thing ı don't understand why magnetic field turns around the cable and what is its effect ?

[@PhysicsMadeEasy]

As discussed in the video, the shape of the magnetic field lines around a cable with current is justified by the behavior that a moving charge located close to that cable has (to explain such behavior, the field line need to be perpendicular to the direction of the current, and to make sure of that, perpendicular to the radius of the circle around that current).

[@bsure4]

how does hydrostatic pressure work in a very thin 1/4 tube ? Your videos are excellent!

[@PhysicsMadeEasy]

Hi, what do you mean by 'work'...

[@auseryt]

Because motion is relative and I'm special relativity one cannot distinguish who is moving you would see a moving object length contracting. Hence, even for an observer not moving relative to the cable the moving electrons contract and so do the moving gaps between them.

[@Zilron38]

Very interesting, but what is a field? it seems to be a force applied over a distance of empty space from source A interacting with source B. I don't believe it can not be nothing therefore a field is some sort of reality we have not discovered or understood yet. Does it bend or twist space time or do these particles exists on a different superimposed plane of existence with it's own rules, and/or are there several planes of existence superimposed on each other that are unique to each sub particle type and each plane of existence has it own rules to interact with other planes? maybe we may never know.

[@PhysicsMadeEasy]

Well I know someone that has read about QFT (Quantum Field Theory), haha ! The video here is within a classical physics context, where fields are mathematical tools that model well reality as we experience it. If you dig deeper, like quantum mechanics does, then fields appear to become real, although these are not fields of force but as you say , fields for which a disturbance is perceived as an elementary particle (or more precisely by the effect of its set of properties). As you seem to be enjoying this kind of reflexion, here's some food for thought: Are we sure that it is the fields / particles that exist? or could it just be their properties? And even wilder, maybe what exists is just the interactions (that we perceive being between properties)… Have fun with that lol !

[@Zilron38]

@@PhysicsMadeEasy Thanks for the response :) I definitely do enjoy this reflexion. I always like to understand how things "operate under the hood" and most forces that we can see and touch are pretty well understood and make sense, but my brain just can't comprehend how fundamental forces operate. We know this is how it is, but not why it is. I find it truly fascinating.

[@andrewjustin256]

Would you please confirm what I am saying that "magnetic field is not fundamental but is electric field's interactions that was formerly not comprehended well; thereof, it was given a new name and is essentially an electric field. Moreover we are still stuck with the of Maxwells equations, despite it describes it flawlessly, and there is no such thing as magnetic field".

[@PhysicsMadeEasy]

Hi Andrew, yes, I do confirm... But please note that this is within the context of classical physics. In quantum mechanics, Fermi proved that if the electric charge is quantized, then magnetic monopoles must exist. If such monopoles exist, that would imply that objects could have a "magnetic charge". In that case, I would need to revise my understanding regarding what magnetic fields are: Magnetic fields would be a definite "thing". But we do know that electric charge is quantized... Yet, despite many efforts we never found a magnetic monopole... Physics is really a fascinating on-going investigation.

[@andrewjustin256]

Well, thank you for clearing that but my concept is still nebulous on what you said about monopole. In addition, from Special relativity we can prove that when charge and current in a wire is flowing, the magnetic force is just electric force, but I heard from the word of mouth that from electron spin arises magnetic pole responsible for the magnetic behavior of an element and also ferromagnets, antiferromagnets and paramagnetism. It appears that magnetic field is completely different force. Would you please cast off few lines on that too?

[@PhysicsMadeEasy]

Maybe you haven't seen the 'hidden' part of the video about magnetic dipoles... At the end, after the credits, I improvised a discussion about this. An electron is spinning, and an electron is a ball of charge, thus in an electron there are loops of currents, that generate a magnetic force of the same origin than the one I discuss in the magnetic field video. Moreover, If you look at the shape of the field of an electron, you realise it is a dipole (with a N and a S), not a monopole... Check the video, it might clarify a few things kzbin.info/www/bejne/oniUhYNrYtd-nK8si=Q6tE3dTffDBKKmVS ...

[@robinhooper7702]

Good day. I love physics but I have a question that I just can't find answer to, or perhaps I'm not asking it incorrectly. How is it that I may be able to contact you to ask and clarify my inquiry? Thanks. Oh, and it is not a school lesson question.

[@PhysicsMadeEasy]

Hello Robin, why don't you ask it here? (Don't reply to that comment, generate a new comment, or I might miss it )

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@user-wh3em9xt3s]

Thank you sir I really struggle in ray optics Will u make videos on this topic in future?

[@PhysicsMadeEasy]

Hi, unfortunately, it is not on my plate right now... You may have noticed I really am in an "electromagnetic mood" right now! Maybe when I get out of it... Refraction by a lens, which relates to ray optics, is a topic that interests me, and I might explore in the future, but that is not going to be soon. Sorry.

[@user-wh3em9xt3s]

@@PhysicsMadeEasy It's totally Fine professor I am waiting for next lecture. Thank you

[@Repentforthekindomogiah]

youtube at it again teaching us folk, thankyou

[@PhysicsMadeEasy]

It's not KZbin!!! They are just a platform...

[@Repentforthekindomogiah]

@@PhysicsMadeEasy I didn't mean youtube , i know it just a platform but it's a platform that has access to million of things you cant really find doing a simple search on the web. Or in a classroom So I meant it as a compliment , youtube is teaching us again, meaning I'm learning nice content through youtube , through youtube I'm finding out about different content.

[@Repentforthekindomogiah]

@@PhysicsMadeEasy so when we say youtube is teaching us , we mean it providing what regular classroom can't provide. We don't mean literally youtube

[@Rajbirsingh-ef5mb]

Plz post a video on charge producing em wave with linear acceleration beacuse very very difficult to understand plz plz plz no one knows about it i have seen video which is very old and not understand properly It will helpful for all physics lover

[@PhysicsMadeEasy]

There is a thread that i pinned in one my videos that should help you with that. This is the video: kzbin.info/www/bejne/npyZZKiLndCNfpYsi=YcV9GcBwO9ssQYBQ Go directly to the comment section, in the pinned thread started by visasaarinen6051, we discuss this with some links to simulation videos.

[@waynemccuen8213]

So, we see in a 2 dimensional example a sine wave on a graph. Growing in a positive direction, then getting smaller and growing in a negative direction. In real time, it would be more like a ball growing positive then shrinking then turning inside out and reversing? I've never thought of this before! My mind is blown. I can't think this through! Thanks for confusing me on a higher level

[@PhysicsMadeEasy]

Hi Wayne, you are welcoming for confusing you on the highest level haha :-) I don't really get what you are referring too (What is the on the x and y axes of the sine graph you discuss?)

[@KRSNA_21]

Sir electric potential is work done on unit +ve charge so can we say electric potential is potential energy

[@PhysicsMadeEasy]

You are correct in saying that the electric potential is the potential energy that 1 unit of charge would have, but what you are missing is that this happens only when that charge is placed at a position having that electric potential. Intrinsically it is not the same thing: An electric potential is a property of a position: it tells you the PE that a charge would have when placed at that position, per unit charge (PE = q * V). Potential energy is a property of an object (How much PE it has) I have a video on this: Check it out: kzbin.info/www/bejne/oGSqo4KBp8qSlZIsi=r5I2KqnQwVTyucon

[@sammyapsel1443]

in section 2, i think the effect at 6:51 isn't due to special relativity but because of the rolling shutter effect just fyi.

[@PhysicsMadeEasy]

The two pictures are actually the same picture, one I thinned artificially for illustrative purposes: there is no way at a speed of 5m/s, I would be able to detect the effect. for fun, following your comment, I just calculated the effect: for an object of 1 meter in length, the length contraction effect would have been about a half of a femtometer (that's smaller than the diameter of proton). :-)

[@manudehanoi]

arent magnetism and electric force interchangeable in relativity, such that yes you can say magnetism is a relativistic effect of the electric force but you could say just as well that the electric force is a relativistic effect of the magnetism ?

[@PhysicsMadeEasy]

Well done Manu, I had the same thought when scripting the video. My answer to that is that electric monopoles exist (common electric charges), but not magnetic monopoles. That means that a single system, whatever its size, cannot have a magnetic charge. This is also implied in Maxwell's 2nd equation. In other words, we are not in a chicken and the egg situation: Magnetic fields cannot be the starting point, electric fields are. Of course, there is always the idea that according to Dirac, magnetic monopoles must exist in the universe, (even if there would be only one) .These must be extremely rare because despite much efforts, none have been detected yet. I really like this topic, I might make a video on this. I love the fact that when I research for a video, it triggers questions in me, and thus, gives me ideas for new videos!

[@manudehanoi]

@@PhysicsMadeEasy im not sure I get your point about single systems not aving a magnetic "charge". I could say that a dipole is a single system. I think it's just a matter of instinct, the electric field is just a simpler phenomenon than the mag one, therefore we are tempted to put it higher in the causal chain

[@PhysicsMadeEasy]

@@manudehanoi The instinct you mention is a good one, a version of Occam's razor. As discussed magnetic system only come as symmetric dipoles... thus the "magnetic charge" of such system is always zero... that means that there can be any net magnetic flux across a closed surface (2nd Maxwell law). In the absence of any system that can have a non zero magnetic charge, while net electric charges are common, one would indeed tend to put electric field higher on the causal chain (very good expression btw). I am actually reflecting on this, and may produce a video on these reflections. At the current state of my thoughts, I am starting to consider that what really can be considered as 'existing' is the electromagnetic field, made of two indissociably linked components: electric and magnetic fields... What do you think?

[@manudehanoi]

@@PhysicsMadeEasy I think last i tried to make magnetic calculations it was a fantastic pain in the ass, getting an understanding of the mag field also is, the mag flux is ...Anyways, without being able to prove it, id put it as a consequence of the electrical field.... However I think maxwell put the mag and electric field as coexisting and without any delay between one and the other, plus each time I ask if the light wave propagates because the change in electric field causes a change in mag field and that causes a change in the elec field and so on, I get a different answer....So I gave up

[@mahirbalayev5835]

If magnetic field doesn't exist indeed, then what is magnetic field of electromagnetic wave indeed, could you please explain?

[@mahirbalayev5835]

And if magnetic field occurs due to length contraction, then why is there magnetic field in wave? Could we assume that it occurs due to extending/curving of spacetime?

[@PhysicsMadeEasy]

Hello Mahir, to find a coherent answer to your question, you need to think about the source of the oscillating electric field in an EM wave... It will be an oscillating charge (i.e a charge in motion). it generates an oscillating electric field, and because the charge is moving, a magnetic field emerges too, that will propagate along the oscillating electric field).

[@PhysicsMadeEasy]

Answer to your first question in my other answer. Regarding the curvature of space time, within the framework of our discussion, not really... Otherwise we would have a theory unifying gravity and electromagnetism. Space time might be curved a little bit though as it will be affected by the energy carried by the wave, but the effect would be negligible.

[@mahirbalayev5835]

@@PhysicsMadeEasy does it mean that fields (electric or magnetic) from point source just pull each other because of direction of each field?

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@muntee33]

Woah woah woah, let's walk it back a bit first and establish our understanding from a base line principle. First we must qualitatively explain and demonstrate the elementary component of your preposition. (Which we have not even yet done in any/all of physics yet, so good luck. Haha) And that elementary component is... What IS a field?

[@PhysicsMadeEasy]

Well Muntee, maybe you should explore my channel a little more in depth... and you'll find this haha! There is even a video called 'what is a field?', another called 'what is an electric field' and others that details more physics basics... Note that I agree 100% with your pedagogical approach: make sure that a student has a good grasp of the fundamentals first...

[@kimbowaaloysius1181]

We, therefore, live in an electric universe

[@PhysicsMadeEasy]

A little too general, don't forget gravity, strong and weak forces! But it's true that at human scale, only electric and gravitational forces appear to have an effect. Even mechanical forces are electric in nature!

[@zakirhussain-js9ku]

What is magnetic field made of.

[@PhysicsMadeEasy]

Hi Zakir... check the video :-)

[@The_Green_Man_OAP]

There's a problem with what you are saying. Here is my explanation: CHARGES IN A WIRE ACTUALLY _DRIFT SLOWLY_ , BUT (MASSLESS) WAVES IN WIRES _TRANSMIT FAST._ Therefore, the relative motion is between _parts of traveling waves_ and fixed observer(s), _NOT between moving masses._ So, to clarify: The _relative motion_ in the wire is to do with the _transmission of energy_ (aka _force or impulse:_ two way action/reaction), _NOT_ (one way) _mass transfer._

[@zBrush01]

😮

[@PhysicsMadeEasy]

What do you call massless waves (the official term)?

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@digbysirchickentf2315]

Did you mention who came up with this hypothesis?

[@PhysicsMadeEasy]

Einstein... :-) And it was not really an hypothesis, but more of a result from the theory of special relativity (the latter being based on two postulates that are verified experimentally).

[@digbysirchickentf2315]

@@PhysicsMadeEasy Electrons in a wire move around 4mm per second, hardly relativistic speeds?

[@PhysicsMadeEasy]

@@digbysirchickentf2315 detailed answer here: physics.stackexchange.com/questions/210286/how-can-relativistic-effects-be-the-cause-of-magnetic-forces-when-the-normal-spe

[@digbysirchickentf2315]

@@PhysicsMadeEasy Detailed quackery, this is all BS. Shame on you, show some critical thinking.

[@PhysicsMadeEasy]

@@digbysirchickentf2315 What? Have you looked at the link I told you? (the answer by Emilio Pisanty). The relativistic effect is extremely tiny, and it disturbs in an extremely tiny way a balance between huge amounts of charges (the positive and negative charges within the same a cable...). So the effect becomes measureable. Please be more moderate in your choice of words when you do not agree.

[@vinniepeterss]

cool😢

[@lw5359]

You only just barely touched on it, but I think your explanation of the magnetic field generation in a permanent magnet was quite incomplete, and most likely not correct. Heaviside said the field of a permanent magnet was a point-source phenomenon, not a summation of a bunch of tiny molecular "movements".

[@web_physics]

Moving charge produce magnetic field 😮magnetic force per unit moving charge is magnetic field 🏑🧲

[@PhysicsMadeEasy]

Yes, I guess you could define a magnetic field as the force experienced by a moving positive charge per unit charge and per unit of velocity of that charge, and that for a given relative orientation of the velocity vs that of the magnetic field strength vector.

[@vincecox8376]

Please get tuned into facts, 1. anti gravity is a product of the center field of a magnet. 2. the center of a magnet when vibrated will repel water 3. If you vibrate granite rock with the center field of a magnet at the correct frequency it will turn like butter. that's just the beginning it will play a Hugh part of our country's future. This is only applicable to none iron type material such as glass or plastic. If you have a bar magnet simply tap the center near a trickle of water and watch the water move out of the way. Tap the center field on any none metalic surface and watch it loose weight. You can not use a sign wave type vibration it must be saw tooth . A sign wave signal contains the centerfield, that's what pushes AC and radio signals around the world. A sign wave has three elements on an oscilloscope you only see the two , On a scope you see the positive cycle and the negative cycle you never see the most significant part of the cycle and that is the center field that produces the energy to push the energy forward!!! There is allot to be learned about the magnetic center field .. Please help spred the news ..

[@user-ig9df9sq4h]

​@@PhysicsMadeEasyq I

[@cristig243]

No human knows what a magnetic field is .

[@guitarizard]

I do.

[@aiden_aiden]

what do you mean by that?

[@kennyfordham6208]

Indeed, he explains equations and the movement of electric forces, but there's no specific definition of what that 'force' is. The 'force' can be detected, and it can do what we want it to do, but exactly what it is, remains a mystery.

[@guitarizard]

Veritasium, what is a force.