Question

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 charge of potential difference between the plates.

(b) Obtain the displacement current across the plates.

(c) Is Kirchhoff’s first rule (junction rule) valid at each plate of the capacitor? Explain.

Answer 1

Here,

I = 0.15 A

d = 5.0 cm = 5.0 x 10^-2 m

R = 12 cm = 12 x 10^-2 m

Therefore, area of each plate,

(b) The displacement current is equal to the conduction current i.e., 0.15 A

(c) Yes, Kirchhoff’s first law will be valid at each plate of the capacitor, provided the electric current means the sum of the conduction and the displacement currents.