Question

An uncharged spherical conducting shell surrounds a charge −2q at the center of the shell. Then charge +3q is placed on the outside of the shell. When static equilibrium is reached, the charges on the inner and outer surfaces of the shell are respectively

A +q, −q.

B +q, +2q.

C +2q, +q.

D −q, +q.

E +3q, 0.

Answer 1

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According to Gauss's law which states that Flux of  Electric field = Charge enclosed / epsilon

Flux of electric field = E * surface area.

We know E in the surface of spherical conducting shell = 0.

Therefore q enclosed = 0.

Charge -2q is placed inside the shell, so +2q appears on inside surface of the shell , so that q enclosed within the shell = 0.

+2q comes from the outer surface of the shell, leaving +q behind.

Therefore option C is correct.