Question

Two tiny conducting spheres are identical and carry charges of -18.0 µC and +54.5 µC. They are separated by a distance of 2.61 cm.

(a) What is the magnitude of the force that each sphere experiences, and is the force attractive or repulsive? N (

b) The spheres are brought into contact and then separated to a distance of 2.61 cm. Determine the magnitude of the force that each sphere now experiences, and state whether the force is attractive or repulsive.

Answer 1

a) The magnitude of the force that each sphere experiences is given by Coulomb’s law as:

Because the charges have opposite signs, the force is attractive .

b)

The net charge on the spheres is -18 uC + 54.5 uC = 36.5 uC

When the spheres are brought into contact, the net charge after contact and separation must be equal to the net
charge before contact = 36.5 uC. Since the spheres are identical, the charge on each after being separated is one-half the net charge, = 36.5/2 = 18.25 uC

Since the charges now have the same signs, the force is repulsive.