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just a copy of https://physics.stackexchange.com/q/422286/203741, maybe I'll get answers there


I'm on the way to understand em waves, but I decided, that I need to completely understand a current flowing. Not basics, not in general, I need to understand every trifle. I think, for a lot of people it will be very useful. Post only applies to induced current.

I will write, below, how do I understand things, if it wrong - correct me, and answer question during posting.

How does current induces

According to Faraday law, changing electric field generates changing magnetic field. How, and why does it occurs. Below, you can see fields of charge with $v=0, v=const;a=0,a!=0$.

enter image description here

  • The first case called electrostatics and describes by Coulomb law. If you confused, how does standing charge, that don't lose its energy, generates force, according to classic physics - well, I'm as well.

  • The next one is "constant magnet field", if you here because of questions too, you probably remember about Lorentz force, and now think - where is there perpendicular components? Good question, I don't know.

  • The third is electromagnetic wave, it actually has a perpendicular component, you can see it, it means, that the force there directs perpendicular to "previous line", it clear. Why do line curves by the next wave? Well, it could be intuitively understand, if you see the animation(link in the bot). By the way, if we assume that free electrons in metal would be fixed, and you will wave the wire, it will emit a em wave.

Considering, last case, if we put a charge in right or left, you understand it will move up-bottom. So, I think it explains in fundamental level the phenomena of induction. Lets go to macroscopic scales.

How does current flows

Well, there goes all confusing stuff, like voltage, potential difference, E.M.F, etc..

enter image description here

Lets consider the picture above. Okay, the AC wire in the bottom emits an em wave, the force actually directs parallel to wire near. So, now very attentively: electrons are uniquely distributed in wire - there at all, no places with higher or lower number of electrons. Now there occurs the force only in the bottom part of wire, and electrons in the bottom starts to move right or left.

Why do electrons in another parts of wire start to move? Well, I think it happens by the chain reaction:

enter image description here

Here goes specific questionS:

Is AC current in circuits without parallel connections the same in all points of wire(in one time frame)?

enter image description here

According to all stuff above, if it is true, explain this picture. Why current is maximum where voltage is minimum?


Animation

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  • $\begingroup$ Voltage is induced, not current and that induced voltage will circulate a current if there is a conductiing path. $\endgroup$ – Andy aka Aug 12 '18 at 15:29
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It's not the same in all points of a conductor. Speed of light is the upper limit for the speed with which a change in an electric or magnetic field (and that's what causes the current) can propagate.

Hence, the AC current will have a different phase for different points on the conductor.

I think it's likely you'll encounter these sooner or later, anyway, so: If you want to learn how E- and H-Fields change over time and place, you'll need to understand Maxwell's Equations.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – ACuriousMind Aug 28 '18 at 15:22
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**Plancs' constant will tell you everything you need to know about the EM field". Induction can be complicated. When current is induced it is usually amplified or decreased with transformers. An Electromotive force(voltage) must be present for a current to flow. In this case the only EMF is the induced voltage by the bottom circuit.(C2) If the circuit were plugged-in in America it would change direction 60 times a second and have an average voltage of 120 volts. As the current in C2 begins to rise and fall it generates an electromagnetic field in the 'secondary circuit' (C1) This EMF causes a voltage, thus a current, in (C1). As the current in (C2)begins to change direction so does(C1).Induced circuits have to have AC EMF to work properly.The power of the induced circuit depends upon the closeness of the two circuits, the thickness of the wires and the supply voltages. Your best bet would be to study each part of an induced circuit one by one. Then add them all into a workable schematic. Good luck.

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