Question

A and B are two concentric spheres. If A is given a charge Q while B is earthed as shown in figure. Then :

• A. the charge density of A and B are same
• B. the field inside and outside A is zero
• C. the field between A and B is not zero
• D. the field inside and outside B is zero

Answer 1

The correct option is C the field between A and B is not zero

The charge on sphere $B$ due to ground potential of zero is $-Q$ on the inner surface.

Charge density on $A$ is $Q/4\pi r_A^2$ and that of $B$ is $-Q/4\pi r_B^2$. So two charge densities are not equal.

option A is incorrect.

The two sphere system act as the concentric sphere capacitor.

By Gauss' law, The electric field is zero inside $A$ and outside the $B$.

But it is non-zero between $A$ and $B$.

So option B and D are incorrect.

option C is incorrect.