As, displacement current, $I_{d} = \varepsilon_{0} \frac{d\phi}{dt} \quad...\left(i\right) $ Where, $ \phi =$ electric flux $\because \phi = E . A$ For area, $A =$ constant $ \therefore d\phi = A \,dE \quad...\left(ii\right) $ From Eqs. $\left(i\right)$ and $\left(ii\right)$, we get $I_{d} = \varepsilon_{0}A \frac{dE}{dt} $ So, time varying electric field generates the displacement current
Displacement current is a quantity appearing in Maxwell’s equations. Displacement current definition is defined in terms of the rate of change of the electric displacement field (D). It can be explained by the phenomenon observed in a capacitor.