Physics · Electromagnetic Waves · NEET
No. In the gap of a capacitor there is vacuum or an insulator, so no charge (no electron) crosses from one plate to the other. Displacement current is only the effect of the changing electric field between the plates. It is called a "current" because it produces a magnetic field exactly like a real conduction current does, and it keeps the current continuous around the circuit.
Because Maxwell found that a changing electric field does the same job as a real current: it creates a magnetic field. Its size id = ε0(dΦE/dt) is measured in amperes, and it exactly equals the conduction current in the wires. So for magnetic effects it behaves like a current, even though no charge moves through the gap.
When the capacitor charges, charge piles up on the plates and the electric field between them grows. In the wire the conduction current ic carries charge. In the gap there is no ic, but the growing field gives a displacement current id equal in size. So ic outside = id inside, and the current stays continuous everywhere. For NEET remember: i (wire) = id (gap), always equal.
Ampere's law gave two different answers for the magnetic field near a charging capacitor: pick a flat surface cutting the wire and you get B from the current; pick a surface passing through the gap and you get zero, since no charge crosses. That contradiction meant Ampere's law was incomplete. Adding displacement current ε0(dΦE/dt) makes both surfaces give the same B, removing the contradiction.
Yes. That is the whole point. A changing electric field (displacement current) produces a magnetic field just as a conduction current does. This is why between capacitor plates, where only a changing field exists, there is still a real magnetic field circling the axis. This symmetry — changing E makes B, changing B makes E — is what allows electromagnetic waves to exist.
A parallel plate capacitor of capacitance 20 µF is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires and the displacement current through the plates of the capacitor would be, respectively,
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates,
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the current-like effect of a changing electric field, id = ε0(dΦE/dt), which produces a magnetic field just like a real current even though no charge moves.
In regions where the electric field is changing but no charge moves — most famously in the gap between the plates of a charging capacitor, and in space where electromagnetic waves travel.
Yes, for a charging capacitor the displacement current in the gap exactly equals the conduction current in the connecting wires, which keeps the total current continuous everywhere.
James Clerk Maxwell introduced it to fix a contradiction in Ampere's circuital law near a charging capacitor. It led directly to the prediction of electromagnetic waves.
It explains how a changing electric field creates a magnetic field, which is the basis of electromagnetic waves. NEET asks conceptual questions on continuity (id = ic) and on its magnetic field, so understanding the idea earns easy marks.
