## In This post you will get answer of Q.

A charge q is placed at the centre of the line joining two exactly equal positive charges Q. The system of three charges will be in equilibrium, if q is equal to

Solution:

## For equilibrium of charge Q, the force of repulsion due to similar charges Q should be balanced by the force of attraction due to charge q and

$ frac{1}{ 4 pi varepsilon_0 } times frac{ Q q}{ ( r / 2)^2 } + frac{1}{ 4 pi varepsilon_0 } times frac{ Q^2 }{ r^2 } = 0 $

or $ 4 times frac{ Q}{ r^2 } q = – frac{ Q^2 }{ r^2 }$ or $ 4q = – Q$ or $ q = – frac{ Q}{ 4}$.