Question

Two positive charges of equal magnitude q are placed as shown in the figure. A negative charge of magnitude Q is placed at the centre of line joining them. The value of Q for the whole system to be in equilibrium.

• A. $\frac{q}{2}$
• B. $\frac{q}{4}$
• C. $\frac{q}{\sqrt{2}}$
• D. $\frac{q}{2\sqrt{2}}$

Answer 1

The correct option is B

$\frac{q}{4}$

For q to be in equilibrium

$\Rightarrow \frac{kqq}{(2r{)}^2}=\frac{kQq}{r^2}\Rightarrow \frac{q}{4}=Q$