Three particles, each having a charge of `10 muC`, are placed at the vertices of an equilateral triangle of side 10 cm. Find the work done by a person in pulling them apart to infinite separations.

Explanation

The potential energy of the system in the intitial
condition is
` U= 3xx (10muC) xx (10muC)/(4 pi epsilon_0 (10cm))
`= ((3xx10(-10) C^2))xx ((9 xx10^9 Nm^2 C(-2))/(0.1 m) = 27 J.`
When the charges are infinitely separted, the potential
energy is reduced to zero. If we asume that the charges
do not get kinetic energy in the process, the total
mechanical energy of the system decreases by 27J. Thus,
the work done by the person on the system is -27 J.