Question

Three concentric conducting shells carry charges +4Q on inner, –2Q on middle and +6Q on outer. The charge on inner surface of the outer shell is

• A. 0
• B. 4Q
• C. Q
• D. –2Q

Hint:

Inner surface charge = –(charge enclosed inside).

Answer 1

The Correct Option is D

Step 1: For electrostatic equilibrium, field inside conductor = 0.
Step 2: Charge enclosed by outer conductor must be neutralized on its inner surface. Total charge inside outer shell: \[ +4Q-2Q=+2Q. \]
Step 3: To cancel this, inner surface must have: \[ q=-2Q. \] Hence → (D).