# Electric field in a region with constant potential

1. Mar 20, 2010

### zdotcom

1. The problem statement, all variables and given/known data
When the potential is constant throughout a given region of space, is the electric field in the region also zero?

2. Relevant equations
in a parallel plate capacitor,
electric filed = - delta V / delta d

3. The attempt at a solution
It is difficult to understand how in a given region where the electric potential could be constant. That means at any given location, V=kq/r is the same everywhere and delta v equals zero. I can only relate this to a plate capacitor where the electric field is defined as - delta v / delta d. If delta v is zero, then E=0. Am I on the right track?

2. Mar 20, 2010

### xcvxcvvc

yes. that equation you used comes from the calculus definition that relates electric potential and electric field.

$$E = -\frac{dV}{dr}$$

this equation simplifies to the one you wrote if the rate of change of voltage with respect to displacement is a constant.

So electric field equals the negative of the rate of change in voltage. If voltage is constant, meaning it has a rate of change of zero, electric field also is zero.