# Electric fields in an Inductor

1. Nov 21, 2012

### mathsciguy

En and Ec are the non-conservative and conservative electric field respectively.

I've quoted this from the textbook I'm using (University Physics by Young and Freedman 12th edition).

Now, it seems to me that the author just invoked the assumption that the inductor have negligible resistance and hence it only needs very small electric field (thus approximately zero?) to move the charges through it out of nowhere.

It seems wishy-washy to me, it's very convenient so that we can just advance through the discussion and go ahead with the derivation and come up with a very nice equation. My question is, really, how come the net electric field within an inductor is zero? The proposition that 'the inductor just have a very very small resistance so the electric field is zero' isn't very convincing to me, can anyone expound on this for me?

2. Nov 21, 2012

### Staff: Mentor

Use superconductors if "very small resistance" is not small enough for you. They have zero resistance, and all electric fields have to come from magnetic effects.

3. Nov 22, 2012

### mathsciguy

@mfb: Does that mean that I just have to believe that proposition? I mean, if it's an experimental fact, then I don't have any problems with it. I'm just a little irked by how it's presented to me I guess, or most probably I've missed something crucial.

4. Nov 22, 2012

### Staff: Mentor

It is an experimental fact that you can have setups where resistance is negligible (or even zero).
You can have other setups as well, but they are not discussed in your quote.

5. Nov 22, 2012

### Enthalpy

Only type I superconductors have zero resistance, but are limited to a few mT. Type II superconductors, which are normally used for coils, have a resistance.