If a charge q is placed at the centre of the line joining

• Electrostatics

If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is

1. Q/4
2. -Q/4
3. Q/2
4. -Q/2

Answer

F = q₁q₂/4πεr² 

For equilibrium charges, the net force should be zero.

Select a position of charge q on the line joining Q₁ and Q₂ and use formula of force and equate the sum of forces to zero to find the value of q.

The correct option is B.