Question

Two conducting thin concentric shells of radii r and 3r is shown below. Inner shell is neutral. Find the charge that will flow from inner shell to earth after the switch S is closed.

• A. $\frac{-q}{3}$
• B. $\frac{+q}{3}$
• C. $\frac{-2q}{3}$
• D. 0

Answer 1

The correct option is B

$\frac{+q}{3}$

$V_{in}=0k[\frac{q^1}{r}+\frac{q}{3r}]=0\Rightarrow q^1=\frac{-q}{3}$

Or, $\frac{+q}{3}$ charge will flow from inner shell to earth.