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enter image description hereRecently I got stuck witht the following problem.

Imagine we have uniform a magnetic field which induction points upwards. The fields strength is steadily decreasing. If we put an iron coil perpendicular to the magnetic induction vector, then, obviously, there will be electric current induced in the coil.

However, as I understand, the coil itself is only a 'marker' that displays the electric field lines that actually make the electrons move. It means that the elcetric field is there even when there is no coil. Now the problem: I can imagine some coils being close to each other. It will essentially mean, that it in one of them the current will go one way and in the other - the opposite. How can this possibly be?

I looked at this answer as it is phrased very close to what I want and still I couldn't get the idea. Could the answer be presented in more layman terms .

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    $\begingroup$ How exactly are you imagining these two coils? $\endgroup$
    – GeeJay
    Commented Apr 12, 2017 at 14:10
  • $\begingroup$ I added a picture to the original question. $\endgroup$
    – Алексей Наумов
    Commented Apr 12, 2017 at 16:00

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Given your drawing, equal area loops normal to a uniform, changing field, all we can say is this:

1)The integral around the loops of the electric field dotted into the line element are equal--it says nothing about the direction of the field at any point.

2) (Lenz's law) The direction the current flows is the direction that "keeps the magnetic field going"--in layman's terms.

That current flows in opposite directions where the loops are in the same physical space does not contradict point 1, nor point 2.

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  • $\begingroup$ There is something I miss, I guess. If the current flows in two opposite directions in one point, does it mean that the electric field pushing the electrons points in two oppposite directions? $\endgroup$
    – Алексей Наумов
    Commented Apr 13, 2017 at 9:50
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I think what is missing in the analysis is the charge carriers that carry the current (i.e. the electrons). Electric field would be indeed there, if there is no coil, but without coil there are no charges that could be affected by this field and consequently there is no current. If the two coils in the image are joined together, there will be indeed no current through the central part.

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