1. The problem statement, all variables and given/known data A spherical conductor of radius 2 m is charged to 120V. It is now placed inside another hollow spherical conductor of radius 6m. Calculate the potential to which the bigger sphere would be raised if the smaller sphere were made to touch the bigger sphere. 2. Relevant equations Potential of a sphere = Q / 4*pi*E*r [ E = permittivity of medium] 3. The attempt at a solution The potential of the smaller sphere = Q / 4*pi*E*2 Volts Q= 4*pi*E*2*120 The same value of charge Q is induced on the outer surface of the larger sphere ( and -Q is induced on its inner surface). Therefore, the potential of the outer sphere (before the two spheres touch each other) = Q / 4*pi*E*6 + Q / 4*pi*E*6 Volts [the first value is due to the charge on the inner sphere, and the second value is due to the charge on the outer sphere] When the two spheres touch each other, charge flows from the inner sphere (which is at a higher potential) to the outer sphere till both the spheres reach the same value of potential. I am, however, unable to proceed further to find out the potential to which the bigger sphere would be raised. Could someone please help with a few clues? Thanks.