Question

How much energy does it take to bring two 20mC point charges to within 5cm of each other?

Answer 1

Since the potential energy at infinity is usually defined as zero -

U = K Q1 Q2 / R = [1 / (4 Π 8.85E-12) * (20E-6)^2 / ,05

U = 9.00E9 * (20E-6)2 / .05 = 72 Joules