question_answer

Inner shell is neutral and outer shell carries 2qC of charge. Find the charge which flows between earth and inner shell when switch S is closed.

A)  - q from ground to conductor

B)  - q from conductor to ground

C)  + q from ground to conductor

D)  Zero

Correct Answer: A

Solution :

Charge distribution after induction is shown in figure. V of inner shell \[=\left( \frac{2q}{4\pi {{\varepsilon }_{0}}2r} \right)+\left( \frac{q'}{4\pi {{\varepsilon }_{0}}r} \right)\] \[q'\to \]charge flown from earth to shell or from shell to earth.                        \[V=0=k\frac{2q}{2r}+k\frac{q'}{r}.\]      \[\left( k=\frac{1}{4\pi {{\varepsilon }_{0}}} \right)\] \[\Rightarrow \]\[q'=-q\] Since, charge is negative (- ve) so charge \[({{e}^{-1}})\]are flowing from ground to shell.            So, - q charge flows from earth to shell.