Displacement Current

The concept of displacement current is introduced in electromagnetism to modify Ampère's Law to include situations where there is no actual charge moving in a sheet or volume but an electric field is changing over time. The displacement current density I_d can be described as the product of the vacuum permittivity ε₀ and the rate of change of the electric flux dΦ_E/dt. This rate of change is a time derivative which measures how quickly the electric flux changes, and it is vital for predicting electromagnetic waves' behavior. The unit of displacement current density is Amperes per meter (A/m²), the same as for actual current density in a conductor.