Electromagnetic Waves – Solutions

1) Figure shows a capacitor made of two circular plates each of radius 12 cm, and separated by 5.0 cm. The capacitor is being charged by an external source (not shown in the figure). The charging current is constant and equal to 0.15 A.

(a) Calculate the capacitance and the rate of change of potential difference between the plates.

Solution:

Radius of each plate, r = 12 cm = 12 x 10-2 m

Charging current, I = 0.15 A

Distance between the plate, d = 5 cm = 5 x 10-2 m

Capacitance of a capacitor, C = ε₀A/d

Where, ε₀ = permittivity of free space

A = πr² = area of each plate