question_answer

A hollow metal ball 8 cm in diameter is given a charge \[-4\times {{10}^{-8}}C.\] The potential on the surface of the ball is

A)  zero                                     

B)  -90V

C)   -9000V                               

D)  -900V

Correct Answer: C

Solution :

                 When n identical resistors are connected in parallel, the effective resistance is                                            \[R=\frac{r}{n}\]                                               ... (i) When connected in series, the effective resistance is                 R = nr                                    ... (ii) From Eqs. (i) and (ii), we get                 \[R=n\times Rn\] \[\Rightarrow \]               \[R=R{{n}^{2}}\]