Displacement Current

It is a quantity appearing in Maxwell's equations that is defined in terms of rate of change of \(D\), the electric displacement field.

It has the same units as electric current density, but it is not an actual current of moving charges, but a time-varying electric field. In physical materials, there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization.

This was an important addition to Ampere's laws by Maxwell, and has been crucial to explain many phenomena, including Electromagnetic Waves.