question_answer

In the given figure distance of the point from A where the electric field is zero is                                                                       [RPMT 2000]

A)            20 cm                                      

B)            10 cm

C)            33 cm

D)            None of these

Correct Answer: C

Solution :

             Suppose electric field is zero at N. Hence Which gives\[{{x}_{1}}=\frac{x}{\sqrt{\frac{{{Q}_{2}}}{{{Q}_{1}}}}+1}=\frac{80}{\sqrt{\frac{20}{10}+1}}=33cm\].