The Electromagnetic field, how Electric and Magnetic forces arise 

Oh Thanks a lot for these clarifications! I just got this video in my recommendation. Glad to see it :)

Hi, I'd like to ask you to clarify even better the stationary wire problem. You say that electrons are contracted in such a way that the electric charge is zero when electrons are moving, but claiming so it should imply that when they are not moving they should be even more spaced out (less contracted), which means that the wire has less electron density than proton density in this case. How can the electron density be always the same (resulting in a no electric charged wire) if there is contraction when electrons are moving and no contraction when they're not moving?

For those, who have a question which I had "how did these electrons become 'spaced' just by applying current?", there is a good analogy: car traffic becomes more spaced after traffic lights turn green, because the first car started moving earlier than the second one, the second one earlier than the third one and so on. Just like cars, some electrons are affected by the electric force that creates current earlier than the other ones, since electric force is not immediate and propagates from some point (or multiple points) with the speed of light. And just as I wrote that, another question arose: where do electrons find this 'extra space' if they didn't have it initially? Unlike cars, there is no 'first electron' with empty space in front. Also, electrons on the 'forward front' of electric field propagation start moving earlier than ones in front of them, creating an even denser volume of elecrons which can also play the role just after the current started. I'm confused(

thanks for clarifications, for the atractive forces I was thinking if they were sharing somehow virtual photons with negative mass/momentum hahahaha.

I get the part about the virtual photons repelling electrons, but you didn't make an analogous model for the virtual photons to cause electrons and protons to attract. What causes this attraction?

the real question is why does the magnetic force equation look like the Coriolis force equation?

The fact that it requires Relativity (even if the simplified case of Special Relativity, GR doesn't mix well with QM yet) probably spooked your teachers. Most people, even educated ones, have serious trouble with Relativity, more so at mixing it with Quantum Mechanics, which at the core remains an unsolved problem. Maxwell himself necessarily did not understand the "how" it happens (he inspired Einstein and not the other way around) but only the "what" happens.

@@LuisAldamiz *Special* relativity has been fully integrated with quantim mechanics, it's called Quantum Field Theory. It's only general relativity (the one about gravity) that is problematic with QM.

Fun fact, it was Feynman who was the 1st to describe this phenomena using SR

@@Ecl1psed276 exactly. Dirac combined SP and Quantum Mechanics.

Agreed it's in a nutshell on steroids!

Indeed

It's not even close

Hands down

But worst video in their catalogue

good to see you here. Love your channel too

Thanks a lot!

But it’s a quantum ball.. right? My brain tickles.

Very glad you liked the explanation! Thank you very much for your support!

@B.L.A. “those of us with formal education” 🤓

@@kevinflaherty1 so what? You’re jealous of people who pass such high classes that you decide to use the elementary school method of calling them a nerd?

When someone calls you a nerd, they just can’t accept that you may be more intelligent than them. So they find ways to insult you and get more attention for themselves

@@kevinflaherty1 cry harder ignoramus :)

Modern science isn't correct..... All energy and matter in one simple explanation.... here goes... First we have a radio wave all the way to gamma waves which in turn create hydrogen then from there everything is basically a compound of hydrogen and will decay back to hydrogen before turning back to gamma waves..... There are no free moving electrons within matter.... I use this analogy to simplify it in my mind..... imagine a line of people standing a mile long (each person represents a copper atom in a wire) the first person starts a Mexican wave at one end ( the source ) , as the information propagates along the line ( by exciting each atoms magnetic field ) you would see an continuous wave of the peoples arms transferring the charge/information back and forth but the atoms and electrons don't actually move at all..... Think about it, from the source where electricity is "generated" to the ultimate end use, there's various breaks in chain of that electricity, it goes through controllers, transformers, all sort of components.... the transmission happens because of the magnetic field strength of the atoms in the wire being increased and decreased, not because of an actual "electron" flowing anywhere....

yeah, fully concur, until you understand the mechanics , any equation won´t make sense

@@absolute___zero Well said brother. Just mugging up formulae without proper Intuition and Visualization is not true learning.

suhlas :)

Shadilay

KKK

Same

same

very much the same. He seem to cover conventionel topics, but from a new angle, which somehow also makes it easier to understand

they look like the math says they look like

@@DrDeuteron Then what in the hell is a virtual photon ??? A photon that both repels and attracts ? Why would two same charges make possible fror them to appear ??? Also when you say something exists for such a short time it actually DOESN'T exist I'd say you got some nonsense on your hands .

@@alokinzna that's a good question. So in Quantum Electrodynamic (QED), one considers scattering amplitudes. E.g: Moeller scattering (e-e- --> e-e-) or Bhabha scattering (e-e+ --> e-e+), which differ by repulsion vs. attraction. In QED, the Feynman path integral says the EM/electron field takes all possible configuration between initial an final states...which is not solvable exactly. Instead, on considers "perturbation theory", and you approximate the exact solution with a power series in powers of the fine structure constant (alpha). The first term (called "tree level") has a configuration that is the exchange of a so-called virtual photon. That is what a virtual photon is. A term in a power series expansion of QED amplitude. At this level, repulsion or attraction isn't really a thing. If you look up Moeller and Bhabha scattering on wikepdia, they work out the amplitudes in QED, and you will see they depend on (iq)^2 with q = -e or q = +e as needed, and then to get a probability you square the magnitude of the complex amplitude, so the sign just disappears....nevertheless it works. Moreover, in Feynman diagrams, energy and momentum are conserved at all points in the diagram, so the virtual photon can have very unusual kinematics. For instance, for two electron scattering back-to-back in head on collision, the photon has zero energy buy large momentum. That means the mass squared in negative. weird for a photon. Meanwhile in electron positron annihilation in the same kinematics, the photon as huge energy and zero momentum...so it is at rest. Weird for a photon. Basically: the virtual photon can have negative, positive, or zero energy or momentum...so it repels if it needs to repel, and attracts if it needs to attract. So with that, virtual photons are just mathematical things that approximate quantum field configurations. It sounds like BS, but when you use them to calculate "the electron g-factor", experiment and theory agree to 13 (or 14) digits...which is the most accurate and precise calculation in ALL of science. It represents decades of theoretical and experimental work by hundreds (or more) people, and it is remarkable.

@@DrDeuteron You know this is sorta strange . When talking about gravity you can at least come across the terms Higgs field or Higgs boson . How is it that getting the details of magnetism is this difficult and obscure ? Is this a case where we have the detailed description in the form of math as to what is happening but don't know REALLY what is happening ?

And that's why I never actually understood how it worked until now (well, I'm not sudenly an expert now). Other explanations take fields as a given and just try to expand on them.

what do you mean field? Because if you mean Quantum Fields (Which the Electromagnetic and Electron Field are) then yes virtual particles are just visualizations of the interactions of the field.

When we learn of macroscopic things feeling electric forces, the electric field is seen as a bookkeeping device: They are the answer to the question "how much force is felt here?, regardless of the charge of a particle to feel it, which may or may not even exist here" Similarly, we can think of elementary particles, as tangible things that move around in understandable ways. When two electrons toss photons to each other, they create a recoil "force". Neat! Again, we build an electric field as a bookkeeping device. Maybe even a quantum electric field. That is a nice intuitive way to understand what is happening. But if I understand it correctly, physicists believe that the fields are more real than the particles, which are the bookkeeping devices. Because that belief fits better with what we know about reality. That might explain it: we want to be thaught in particles, because particles make sense to us, ...but we are thaught in fields by people who see the fields as real, and thus want to explain how the easy-to-understand particles come from them. We stuggle with the shift in perspective. ____________________________________________________________________________ I do not fully understand why fields must be real and not the particles. All below can be wrong and all sorts of ways. But here is what I understand of it: Macroscopic: The electric and magnetic fields can have ripples in them, that travel at the speed of light. This "light" can exist even without charges around at all. So it seems the fields aren't just bookkeeping the effect of charged things that exert force. The circuit of unknownsource-veritasium shows that you don't need charged particles to push on each other through a circuit. The effect of flipping a switch would have to take a light-year long detour to reach a lamp only one meter away, taking a year. But instead, the electromagnetic fields that live everywhere carry the signal to the lamp across the gap in the wire. Long before the edge of the circuit knows that something has changed. In general, I believe there are effects that an electrical circuit cannot predict, because the circuit exists in space, with the wires being close to each other and all that. Quantum: Virtual particles are weird particles. Two electrons tossing photons back and forth is fine, but the analogy breaks for an electron and a proton. When a proton catches a photon from an electron, it recoils towards the electron instead of away, and vice versa, and that is just weird. The relation between energy and lifetime comes from this: the virtual photon has to fly under the radar of heisenbergs uncertainty relation, which is a limit on what we can detect with accuracy and certainty. But why should it fly under the radar? Can't we sometimes see measurable photons being tossed back and forth, in a proper scientific experiment? I believe that charged particles don't glow, unless sped up or down. It is said that virtual photons aren't real photons. They are ripples, perturbations, in the quantum electromagnetic field. When those ripples exceed heisenbergs uncertainty relation, they are seen by detectors. And can thus be called "real" photons. Any other feature -- rippleshaped or not -- can be broken in a sum of smaller ripples, which we can argue are still photons -- ripples --, but they travel under the radar. This helps to calculate what the fields do in an interaction, by looking at scenarios of virtual particles doing what particles do. In theory, we need to mix all scenarios by likelyhood, to know what happens. In practice, we mix only the more likely scenarios as an approximation. Either way: the virtual particle is now the bookkeeping device, and the field is the real thing.

@@nielskorpel8860 you cannot detect them because they are pure nonsense. Photon exchanged between proton and electron has negative momentum for proton and positive momentum for electron. Another problem is - why does any field even exist? If it were for virtual particles to exist, you could imagine how in uniform electric field one pair of electron-positon popping out of nothingness, creating a circle, and then disappear. Not a big problem, but inside said circle, electric forces of the field are balanced out by formentioned particles. You create a "bubble" with no force at all. Now go on with as many bubbles you like, and whole field disappears! It's absurd, because there is no virtual photon or electron, but quantum field. And all the sudden it all makes sense.

@@Etrexum Actually, that's a far more accurate picture. The virtual particles are just oscilation in the underlying field. Oscilation caused by the real electron themselves. Nothing more.

Thank you so much, glad you liked it!

Amazing video. I understood how the virtual photon picture, with the recoil, can explain a repulsive force. But I find it hard to understand how the virtual photon explanation applies to an attractive force between opposite charges. By the time the video speaks about attraction between opposite charges, the virtual photon picture no longer makes an appearance.

@@elpak it looked like the attraction was depicted by two virtual photons being emitted simultaneously by the electron and proton, and then meeting in the middle. But yeah no intuitive explanation was given for the electromagnetic attraction as it relates to that illustration.

​@@ScienceClicEN Modern science isn't correct..... All energy and matter in one simple explanation.... here goes... First we have a radio wave all the way to gamma waves which in turn create hydrogen then from there everything is basically a compound of hydrogen and will decay back to hydrogen before turning back to gamma waves..... There are no free moving electrons within matter.... I use this analogy to simplify it in my mind..... imagine a line of people standing a mile long (each person represents a copper atom in a wire) the first person starts a Mexican wave at one end ( the source ) , as the information propagates along the line ( by exciting each atoms magnetic field ) you would see an continuous wave of the peoples arms transferring the charge/information back and forth but the atoms and electrons don't actually move at all..... Think about it, from the source where electricity is "generated" to the ultimate end use, there's various breaks in chain of that electricity, it goes through controllers, transformers, all sort of components.... the transmission happens because of the magnetic field strength of the atoms in the wire being increased and decreased, not because of an actual "electron" flowing anywhere....

They both use different approach and they also complement each other. Veritasium use more day to day exemple as scienceclic is more text book style Both style have it's audience. Also electroboom and veritasium would be furious that it does show the electron moving in the wire 🤣

@@KevenGelinas [I think Electroboom is smarter than that] Electrons _do_ move in the wire, but in a sort random brownian-like motion, albeit with a net drift. If that were not the case, it would be impossible to charge a capacitor, and for it to keep its charge on isolation. I'm sorry, but I stopped watching Derek after the quality of his exposition suffered inversely with his growing talent for attracting web-traffic and calculated controversy: "I'm afraid people misunderstood my video on X." (Then other youtube expositors praise Veritassium's revised X version out-of-beta-test..., generating more traffic). Derek could squeeze a glass of juice from a desiccated orange.

im not a big fan of veritasium lol. I love a good visually animated example narrated by a calm voice. That way your attention isn't interrupted by looking at someones face haha. (Theorganicchemistrytutor, threeblue1brown, khan academy, in a nutshell,..)

if the apple is perceived as still, the direction of motion of the wire is leftwards. The protons move leftwards in the direction of motion because the wire is moving leftwards. These similar motions add onto each other out and net leftward motion is greater. Therefore, wrt. to the stationary apple, protons move faster. Increased speed wrt to the stationary apple is what causes the contraction, as per special relativity. In contrast, the electrons move rightwards, opposite to the direction of motion because the wire is moving leftwards. These contrasting motions try to cancel each other out and net rightward motion is smaller. Therefore, wrt. to the stationary apple, electrons move slower. Decrease in speed wrt to stationary apple is what causes the expansion, as per special relativity. You can compare the change in resultant speed of both particles @6:57. Hope this helps!!

@@chad7928 I actually meant the case where both wire+apple are stationary! So, protons stationary wrt apple. So from the point of view of the apple, stationary protons and moving electrons should make the electrons appear "denser" in the wire relative to the protons, no?

Something main professors should learn from

It's very well presented, but next week it will be gone from our minds. Somehow reading a book works better for remembering this stuff!

@@ab8jeh nah these type of videos give the sense how things are actually layered and related to eachother. The content isn't meant to really be remembered but rather is a tool for interpretation; such that the content you eventually do have to remember can be remembered and understood easier

Because it's wrong.

Very glad you like them!

The video didn't claim any specific speeds or effects. However, it is true that this effect is only noticeable at high fractions of the speed of light, which means for actual electrical circuits it is never actually observed because the electrons are barely moving in relation to the protons. So even an object moving very fast next to the cable will see the photons and electrons traveling in the same direction at nearly the same speed. This is more of a thought experiment.

😅😅

For your first question, we suppose that the wire is neutrally charged in the initial frame of reference. This means that there would be slightly less electrons than protons in the wire, such that, when the electrons move, they get contracted exactly the right amount to compensate the protons. For your second question, there is indeed no good image that I know of to picture attraction by virtual particles. One analogy I like to use it to imagine that the two people are not exchanging a ball but rather a boomerang : they throw the boomerang towards the exterior, which pushes them back closer to each other.

In the stationary reference frame, where only the electrons are moving, it is supposed that the electrons and protons are equally dense in the wire. That's the setup for the thought experiment. It's a little confusing because he first showed the electrons as motionless as well, but the setup is really that they are in motion and equally dense as the protons.

Because the wire at rest is electrically neutral. We can just measure this. You can try to think about what happens when you turn on the current that ensures this but that gets _really_ complicated. The upshot is that the wire is neutral before you turn on the current and once the current is stable, but not necessarily while the current builds up. I think ScienceClic have a video where they mention a boomerang analogy. Instead of throwing a ball at each other, they throw a boomerang away from each other which then travels around and hits the other particle from the other side, each time imparting momentum that pushes them together. Otherwise you just sort of have to accept that virtual particles can have negative momentum.

@@ScienceClicEN Gotcha! That helps, thanks for replying, and thanks for the jaw droppingly mind-bending content you deliver with every video!

The amazing thing is the author is 24 year old, and my feeling he has an understanding of Physics that is often superior to many Physics professors.

To explain it this well, you have to understand it this well first, and it's clear that not many people out there do.

Protons emits photons. Whereas electrons absorb photons. This phenomenon creates a momentum within the proton and electron and thus they attract each other

I was wondering that too.

@@moukafaslouka4796 hopefully someone in the know will pop into this comment thread in the near future :D

I agree, regarding: "It was apparent how repulsion between like charges works but i didnt really understand how two particles could attract each other by exchanging photons." It seems the explanation of attraction was neglected, as the motivation of throwing the ball from the intro doesn't seem to neatly map onto an exchange of photons between opposite charges, it begs further discussion. Also, regarding Maxwell's second equation-it's not a fundamental law that the equation equals zero, but rather the value was set to zero as a choice to reject the magnetic monopole. Dirac has some things to say about this: en.wikipedia.org/wiki/Magnetic_monopole#Dirac_string -- I'm not quite as optimistic about their existence, but they are not categorically forbidden under the theory and equations of electromagnetism (kind of the opposite).

@@Alex-nb7on I was also troubled, and was looking for a critical comment among the flurry of unbridle praise. But I think the implication is buried between the lines that _virtual_ particles are able to be endowed with the property of negative momentum. Since virtual photons are nothing but constructs arising from the field, and not particles _at all,_ they escape the prescription that they must necessarily have mass, and even a _proscription_ that they cannot have a negative mass.

Search "magnetic monopoles and PBS spacetime" here on youtube if you haven't done so by now. They have a great video on the topic of monopoles and how quantum mechanics suggests that they might be possible (despite classical theory indicating otherwise).

I am not a physicist but as I understand it virtual particles have no requirement to be created before absorbed (so it will travel back in time). So when its taken before created then it can create attraction.

I had the same question. The Virtual Photon seems to be an abstraction to try to explain electric forces en.wikipedia.org/wiki/Virtual_photon Virtual Photons with negative energy causes attraction ... but IMHO is kinda hand-wavy

I have the same doubt

Because this is all garbage suedo science. Absolute rott. Gobbledygook. Only the feeble minded go " oooo so thats how it works " I hope he clapped his hands to wake his audience up at the end. What a joke.

He explains it very well in the video. They cancel each other out until movement is introduced. It's right there in the video. Were you not paying attention?

The virtuality of virtual photons does not lie in their fleeting evanescent existence _as particles._ They are not particles at all. Their virtuality is in that they are imposter-artifacts in the field that temporally behave with real particles as though they were the real deal. It's the difference between a dollar bill and a check for one dollar. They can thus have peculiar properties such as no momentum, or even negative momentum (=they can behave like a 1-dollar IOU... just the opposite sense of a dollar) As long as the latter doesn't bugger-up the particle's otherwise photon- _like_ attributes with respect to the other actors in the interaction, yes, it can exert a yank, instead of a yeet before it disappears. Because it is not a real particle, it doesn't have to have real mass, and can seem to defy Newton.

Good question, don't get it either...

Agree. Also, electrons speed in a wire is around 10 centimeters per hour. Not enough for any relativistic effect.

Yes, this is exactly what I am wondering about. It should not matter what is moving against what. All movement are relative therefore it seems to me that stationary positively charged apple should be attracted to wire with flowing electricity by imbalance of forces in the same manner as moving charged apple. Any explanation what I get wrong?

@@balabuyew I think the explanation for this is that due to the sheer number of particles involved, summing the extremely small contribution of each one results in a significant overall effect. Though, I'm not too sure about the details, electric current is measured in Coulombs/sec, meaning that given even a small drift velocity, the number of particles moving past a given point in the wire is quite significant: approximately the equivalent of 6.242 x 10^18 electrons per second.

Finally some peeps are questioning this garbage !

Yes there is indeed a caveat with this pop-science approach, one should keep in mind that this image with virtual photons is just an analogy, but what really underlies all this are the maths of quantum electrodynamics. As you noticed, it is difficult (and not very judicious anyway) to determine the cause/effect relationship between how far and how energetic a virtual photon can travel/be.

@@ScienceClicEN How electron knows in which direction it should fire a "virtual photon"?

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