question_answer 36)

A small sphere of radius r1 and charge q1 is enclosed by a spherical shell of radius r2 and charges q2. Show that if q1 is positive, charge will necessarily flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge q2 on the shell is. 

Answer:

Charge resides on the outer surface of a conductor. So the charge on inner sphere will flow towards the shell through the conducting wire. Moreover, from Gauss' law, no electric field exists inside a Gaussian surface and also the charges enclosed by a closed surface only contribute towards the field. So q2 does not matter in this case. If q1 is positive, potential difference is also positive.