Question

Two oppositely charged identical insulating spheres, each 59.0cm in diameter and carrying a uniform charge of magnitude 165?C , are placed 1.20m apart center to center.

If a voltmeter is connected between the nearest points on their surfaces, what will it read?

Answer 1

The amount of charge that can be placed on a capacitor is proportional to the voltage pushing the charge onto the positive plate. The larger the potential difference (voltage) between the plates, the larger the charge on the plates:
                  Q = C V

The constant of proportionality is called the "capacitance" and is proportional to the area (A) of one of the plates and inversely proportional to the separation between the plates (d):
                C = e A / d
for a parallel plate capacitor,
where e is the permittivity of the insulating material (or DIELECTRIC) between the spheres.

e = 1.0059

A = area = 4*pi *r*r = 4*3.14 *59/2 *59/2

A= 10930.34 cm ^2

d = 120cm

C = 1.0059 *10930.34 /120

C = 91 mic ro Farad

V = Q/C = 165 / 91 = 1.8 V