(a) Capacitance of the parallel plate capacitor C =
ε0A
d
=
8.85×10−12×π×(12×10−2)2
5×10−3
C = 80.1 × 10−12 F = 80.1 pF We know Q = CV I =
dQ
dt
= C
dV
dt
So,
dV
dt
=
I
C
=
0.15
80.1×10−12
= 1.875 × 109 V s−1 (b) The magnitude of displacement current is equal to conduction current. ∴ Id = I = 0.15 A (c) Yes, Kirchhoff’s first law is very much applicable to each plate of capacitor as Id = I. So current is continuous and constant across each plate.