What is displacement current?
Answer
Displacement current is the current-like quantity produced by a changing electric field, given by displacement current = ε₀ × rate of change of electric flux.
The working
Why it was needed
Maxwell noticed that Ampere's law failed in the gap of a charging capacitor, where no conduction current flows yet a magnetic field still exists.
Definition
Displacement current is not due to moving charges but arises from a time-varying electric field between the capacitor plates.
Formula
Displacement current I_d = ε₀ × (dΦ_E ÷ dt), where ε₀ is the permittivity of free space and Φ_E is the electric flux.
Significance
It made Ampere's law complete and showed that changing electric fields produce magnetic fields, predicting electromagnetic waves.
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