When a parallel plate capacitor is being charged by a dc battery, why
does a galvanometer show a momentary deflection? Obtain the expression for the displacement current and show how it is related to conduction current in a steady state.
In between the plates of the capacitor due to the time-varying electric field, there is a current. This current is known as displacement current. While charging a capacitor total current is the sum of displacement and conduction current. Due to this current galvanometer deflects.
The electric field between the plates of the capacitor
Electric flux
During charging the charge is varying with time
Therefore change in flux with respect to time
Displacement current
At steady-state, there is no change in the electric field there for displacement current is zero.