Question

Metal sphere A has charge of −Q. An identical metal sphere B has charge of + 2Q. The magnitude of electric force on sphere B due to sphere A is F. The magnitude of electric force on sphere A due to sphere B must be:
A. 2FB. F/4C. F/2D. FE. 4F

Answer 1

To solve this problem we will apply the electrostatic Force equations defined from Coulomb's Law. In general, said force can be defined as,

$F = \frac{kq_1q_2}{r^2}$

Here,

k = Coulomb's constant

$q_{1,2}$ = Charge

r = Distance

The electric force in B due to A is

$F = \frac{kQ(-2Q)}{r^2}$

$F = \frac{-2Q^2}{r^2}$

The force in A due to B is

$F' = \frac{kq_1q_2}{r^2}$

$F' = \frac{kQ(-2Q)}{r^2}$

$F' = \frac{-2Q^2}{r^2}$

Therefore they are the same.

$F' = F$

Correct option is D. F.