Question

An attractive force of 7.2 N occurs between two charges that are 0.20 m apart. If one charge is 4.0 μC, what is the other charge?

Answer 1

F = ko *Q_1 * Q_2 / d^2

Q_2 = F*d^2 / [ko*Q_1] = 7.2 N * (0.2m)^2 / [9.0 x 10^9 N/m^2C^2 * 4.0 x 10^-6C] = 8x10^-6C = 8 microC