A small positively charged ball of mass m and charge  $Q_0$ is suspended by an insulating thread of negligible mass. Another positively charged small ball of charge Q is moved very slowly from a large distance until it is in the original position of the first ball. As a result the ball  rises by h . work done by external agent in the process is  $\left[{10}^{-5}J\right]$ ____  given  $Q=Q_0=1\mu C,m=2gmg=9.8m/{\sec }^{2}andh=1cm$