Question

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

Answer 1

Electric Potential Energy :
The electric potential energy of the system of point charges can be defined as the work required to assemble the system of charges by bringing them from an infinite distance to their present location.
Charge on each particle = Q = $10\mu C$

Distance between the two charges = 10 cm = 0.1 m

The potential energy of the one pair of the charge = $E=k\frac{Q^2}{r}$

Putting all the values

$E=\frac{9\times {10}^9\times {(10\times {10}^{-6})}^2}{0.1}$

After solving

E = 9 J

We have three pairs of charges so the total potential energy of the system = $9+9+9=27J$

Hence, work done in pulling them apart = 27 J