Three equal point charges, each with charge 1.15 μC, are placed at the vertices of an equilateral triangle whose sides are of length 0.650 mm.
What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)

The electrical potential energy is 54.9J

Explanation:

Given that charge q1=q2=q3=1.15*10-6c

The side length is 0.650mm

We are required to find the electrical potential U of the system

Note before the U of the system is the summation of potential energy interaction of the system it is given by

U= 1/4πe[q1q2/r12+q2q3/r23+q1q3/r13]

But since the charges are the same and the distance apart are also the same hence U reduce to

U= 1/4πe(3q^2/r)

We're 1/4πe=9*10^9N.M^2/C^2

U= 9*10^9(3*(1.15*10^-6)^2/0.65*10^-3)

U=54.9J