# Electromagnetism problem

1. Feb 17, 2006

### sachi

We have two hollow concentric conducting spheres which are intially isolated from their surroundings and eachother. they are connected electrically, and the outer is connected to a potential source V, the connection between the spheres is then broken. finally the outer sphere is connected to earth. determine the final charge and potential of the inner sphere.

I think the solution is as follows: when the two spheres are connected eletrically they are at the same potential V. since the two spheres are at the same potential, there should be no difference is charge on them due to Q=CV, where Q is the charge displaced between the capacitor plates (n.b I think this means that both spheres have no charge, but could it mean that they have equal charge?) Assuming for the moment that they both have no charge, then when the connection is broken, the inner sphere remains with no charge but potential V. the outer sphere is connected to earth and therefore has no charge or potential. I'm made a little uneasy by this solution, as it shows that there is no difference in charge between the two spheres, and yet there is a potential difference between them (doesn't this violate Q=CV?). Is it possible for charge to be induced from earth to the outer sphere? thanks for your help.

Sachi