Two equal charges, `2.0xx10^(-7) C` each, are held fixed at a separation of 20cm. A third charge of equal magnitude is placed midway between the two the charges. It is now moved to a point 20 cm from both the charges. How much work is done by the electric field during the process?

Explanation

When the charge is placed at a,
` e_1=72xx10^-4J `
When charge is placed at b,
` e_2=36xx10^-4J `
` work done=e_1-e_2 `
` =(72-36)xx10^-4 `
` 36xx10^-4J=3.6xx10^-3J`