What is displacement current?

 

Displacement current is the current produced by a changing electric field or changing electric flux. It was introduced by James Clerk Maxwell to resolve a logical inconsistency in Ampere's Circuital Law and to prove that electromagnetic waves exist. [1, 2, 3, 4, 5, 6]

The Core Concept: The Capacitor

To understand displacement current, look at a charging parallel plate capacitor. [1, 2]

• Conduction Current (\(I_{c}\)): This is the physical flow of electrons in the connecting wires. [1, 2, 3]
• The Problem: In the empty space between the capacitor plates, there are no physical wires or moving charges. Yet, a magnetic field is detected there. Ampere's law could not explain this missing link because it required actual charge carriers. [1, 2, 3, 4]
• The Solution: Maxwell proposed that the changing electric field (or electric flux) between the plates acts as a "current". He named this the displacement current (\(I_{d}\)). It is exactly equal to the conduction current, ensuring the total current remains continuous across the circuit.