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 \[R=n\times Rn\] \[\Rightarrow \] \[R=R{{n}^{2}}\]