When voltage applied to the capacitor, more charges are supplied to the capacitor and there is a flow of current in the external circuit.
The Fig. 1 shows a capacitor C connected across a voltage 'V' and current 'I' is flowing through the external circuit.
Let charge dq be applied the capacitor in time dt, to increase the voltage across capacitor by dV.
The integral given here can also be interpreted as area under the current curve from t = -∞ to the time t under consideration.
Now, capacitor is filled with good insulation, then how can current flow through it ?
The answer is that current flow inside the capacitor is not because of movement of electrons i.e. it is not a conduction current. In a capacitor, we can assume that an imaginary current flows through the capacitor whose value just equals the conduction current outside the capacitor. This current is called 'displacement current.'
