Electric potential energy, U=14πε0q1q2r12
Given, q1=7×10−6C
q2=−2×10−6C
r12=20cm=0.2m
So,
U=9×109×7×10−6×2×10−60.2
U=−630×10−3J
U=−0.63J
The electrostatic potential energy of a system containing two charges 7 μC and - 2 μC separated by a distance of 18 cm is
At the corners of an equilateral triangle of side 25cm charges 1μC,2μC and 3μC are placed. The electrostatic potential energy of the system is :