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## Homework Statement

A solid conducting sphere of radius 'a' having a charge q is surrounded by a concentric conducting sphereical shell of inner radius 2a and outer radius 3a (please refer diagram)....

Find the amount of heat produced when switch is closed ....

## Homework Equations

## The Attempt at a Solution

I proceeded by finding out the Potential energy(electrostatic) of the system initially and finally and their difference is equal to heat lost....Doing all the calculations i get kq

^{2}/2a as theanswer but answer is kq

^{2}/4a......

So can anyone try and tell me if my answer is correct or not.....

I proceeded as below......

part 1.(before switch is closed)

charge distribution is q in the outer surface of smaller sphere, -q on the inner surface of shell and q on the outer surface of shell.....PE of system at this stage is 5kq

^{2}/6a.

Part 2(after switch is closed)

charge distribution is 0 on the outer surface of smaller sphere and 0 also on the inner surface of shell and q on the outer surface of shell.....

PE of system at this stage is kq

^{2}/3a

Difference between Pe = heat so answer is kq

^{2}/2a....