# Electric potential outside of a parallel-plate capacitor

1. Feb 3, 2014

### manuel325

My book says it is zero, but I don't know where to start , why is it zero ? I have to take an exam in few hours so a simple explanation would be appreciated ( I'm not studying pure physics
Here are the electric fields of the three regions . Thanks in advance

Last edited: Feb 3, 2014
2. Feb 3, 2014

Going by the diagram you provided, the electric field due to the capacitor is zero everywhere outside the parallel plate capacitor, right?

Now, if the electric field is zero, then the work done in moving a charge 'q' from infinity to anywhere outside the conductor would also be zero. Think how can this be related to the potential outside the capacitor.

3. Feb 3, 2014

### ehild

The electric field is zero outside, which means that the potential is constant. The potential changes from one plate to the other. The potential is constant everywhere on a metal plate. If the left plate is at zero potential, and the potential difference between the plates is - say 10 V, every point of the right plate is at 10 V potential. As the electric field is zero outside, the electric potential is 10 V to the right from the capacitor. But these are strictly true for infinitely large plates only. Near the edge of the plates the electric field is not confined to the space between the plates, and far away the field is similar to that of a dipole, and tends to zero as the distance increases.

ehild