0
$\begingroup$

When we try to find the electric field between the capacitor plates, what is the right way to do it? This is one of the ways I've seen and I don't understand why:

enter image description here

Using a Gaussian cylinder on the positive metal plate, E inside is zero while E outside is $ \frac { \sigma}{ \epsilon_0}$

But from what I know about conductors is that the charge uniformly spreads itself out on the surface, not only on the bottom, so why do we take a cylinder that only takes into account the charge on the bottom and not on the top as well?

Improve this question
$\endgroup$
3
  • $\begingroup$ So the electric field due to one metal plate without taking into account the other metal plate, should be $E=\frac{\sigma}{2\epsilon_0}$ , correct? $\endgroup$
    – user141410
    Commented Jul 9, 2019 at 19:18
  • $\begingroup$ @cazanova yes it is correct for a isolated metal plate $\endgroup$
    – Nitin Shaji
    Commented Jul 9, 2019 at 19:47
  • $\begingroup$ Yes, that is correct. I have deleted my comment and have posted it as an answer as I think it pretty much answers your question. $\endgroup$
    – user87745
    Commented Jul 9, 2019 at 20:29

1 Answer 1

Reset to default
0
$\begingroup$

You are implicitly taking care of the fact that you have charges on the other plate as well. You are doing it when you assume that $E$ is zero outside (i.e., below the bottom plate). Otherwise, you would have $E=\frac{\sigma}{2ϵ_0}$ both above the bottom plate and below the bottom plate.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.