Module 3 : MAGNETIC FIELD
Lecture 20 : Magnetism in Matter
  Example 25 :
  A parallel plate capacitor with circular plates of radii 10 cm separated by 5 mm is being charged by an external source. The charging current is 0.2A. Find (a) the rate of change of potential difference between the plates and (b) the displacement current.
  Solution :
The capacitance is $C = \epsilon_0A/d = 55.6\times 10^{-12}$ F. Given $dQ/dt = CdV/dt = 0.2$, $dV/dt=3.6\times 10^{11}$ V/s. The displacement current is
 
\begin{displaymath}i_d = \epsilon_0\frac{d\phi_E}{dt} = \epsilon_0A\frac{dE}{dt} = \frac{dQ}{dt}=i\end{displaymath}
  Thus the displacement current is 0.2 A.

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