Displacement Current

Ampère's law, in its usual form, does not work in places where the current changes with time and is not steady. Thus, Maxwell suggested including an additional contribution, called the displacement current, I_d, to the real conduction current I.

Ampere's law states that the line integral of a magnetic field along a closed curve equals the permeability of free space times the net current passing through the loop.

Consider a parallel plate capacitor connected with a battery in a charging condition.

Applying Ampere's law to the shown Amperian loop with two surfaces gives two ...