Question

The charge on a small conducting sphere, kept inside another large conductor is q. The charge on the bigger sphere is Q. The final charge on the smaller sphere after closing the switch S is

• A. q
• B. Q - q
• C. $\frac{q+Q}{2}$
• D. zero

Answer 1

The correct option is D zero

The charge on the inner sphere when the switch is closed becomes zero.
Potential is the work done in bringing a unit positive charge from infinity to the concerned point slowly.
For inner sphere, no matter how small charge it contains, its potential will be higher than that at the outer sphere because to bring a unit positive charge upto inner sphere we necessarily have to bring the charge upto outer sphere first.
So, the charge will flow from inner to outer sphere until the charge in inner sphere becomes zero.