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 two corners. If the net electrical force on Q is zero, then Q/q equals:     [AIEEE 2009]

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

B) - 1

C) 1

D) \[-\frac{1}{\sqrt{2}}\]

Correct Answer: A

Solution :

[a] \[\frac{KQ}{2{{a}^{2}}}=\sqrt{2}\frac{Kq}{{{a}^{2}}}\]

\[\Rightarrow \]\[\left| \frac{Q}{q} \right|=2\sqrt{2}\]

So, \[\frac{Q}{q}=-2\sqrt{2}\]