# What happens to a conducting ring when exposed to an electric field?

It might be a silly question, but one of my friends just got asked this question at an oral exam, and he could not answer it, and didn't receive the answer either (Or at least he forgot).

And I've been thinking a while, and I'm not sure what would really happen.

If I take, lets say a wedding ring, made from a conducting material, placed it on a table, and turned on an external electric field, what would happen ?

The inside of the ring is field free, right ? So does anything even happen, and if so, is it only on the surface of the ring ?

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## 1 Answer

The answer depends on some factors:

1. Orientation of field.
A.If your field is horizontal and passes from the wedding ring, charges will be induced on the ring and it may/may not move depending on the field strength.
B.If your field passes vertically from the wedding ring, then if the thickness of the ring is negligible, nothing will happen.
C.If your field is it an angle then the ring may rotate and move, just rotate, just move or may do nothing, again based on field strength.

2. Field strength.
A. If you apply an high electric field in horizontal direction and somehow keep the ring fixed, the induced charges may jump through the air.
B. If you keep on increasing the strength of electric field there will be a time when the ring will be ionised, but that would not be practical.

3. If you apply a time variable field of sufficient strength the ring may start vibrating.

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If the charges are static, why would they jump (I'm interpreting "jump" to mean that the charges recombine by arcing)? Unless you mean that the charges escape the material to continue travelling along the direction of the E field. – Lenzuola Jan 16 '14 at 21:39
I mean sparking, the induced charges will be near each other.In high electric field, the nearby air may already be ionised or the charges can become so extremely high that they jump like an electric shock/arc. – Rijul Gupta Jan 16 '14 at 21:41
But why would they want to travel in the direction opposite the electric field that separated to begin with? I mean, if the field is AC, sure. But with DC? – Lenzuola Jan 16 '14 at 22:07
I am truly sorry, I drifted while writing the comment, in my answer I write the charges may jump by that I meant something like corona loss. – Rijul Gupta Jan 16 '14 at 22:10