Question

A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to:
A. `Q//4`
B. `-Q//4`
C. `-Q//8`
D. `Q//8`

Answer 1

Correct Answer - B
For equilibrium net force must be zero
`i.e." "1/(4piin_(0))(Qq)/((r//2)^(2))+1/(4piin_(0))(Q Q)/r^(2)=0`
`therefore" "q=(-Q)/4`