Displacement Current

As explained in NCERT Class 12, Chapter 8 (Electromagnetic Waves), Maxwell realised that Ampere's circuital law was incomplete because in the gap between capacitor plates there are no moving charges, yet a magnetic field is observed. He introduced the displacement current, defined as I_d = ε₀ (dΦ_E/dt), where Φ_E is the electric flux. This term arises purely from a time-varying electric field, not from any physical flow of charge. While the capacitor charges, the electric field between the plates increases, so the electric flux changes and produces a displacement current exactly equal in magnitude to the conduction current in the connecting wires, thereby maintaining continuity of the total current. Conduction current due to free electrons cannot flow across the vacuum or dielectric gap, so it is not the answer. Magnetisation current is associated with bound currents in magnetic materials and is irrelevant here. Eddy currents require a conducting loop in a changing magnetic field, which is not the situation between capacitor plates. A consistency check: the displacement current keeps the total current identical throughout the circuit, so Kirchhoff's junction rule is preserved, confirming the choice.