question_answer

A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each of the other tow corners. If the net electrical force on Q is zero, then Q/q equals:     AIEEE  Solved  Paper-2009

A) \[-2\sqrt{2}\]

B)        -1                           

C)        1                             

D)        \[-\frac{1}{\sqrt{2}}\]

Correct Answer: A

Solution :

\[\frac{KQ}{2{{a}^{2}}}=\sqrt{2}\frac{Kq}{{{a}^{2}}}\] \[\Rightarrow \]\[\left| \frac{Q}{q} \right|=2\sqrt{2}\] So, \[\frac{Q}{q}=-2\sqrt{2}\]