Displacement current
(E12.1.1) E12.1 · Displacement Current →A term added to Ampère's law, proportional to the rate of change of electric flux, that accounts for the magnetic field observed between charging capacitor plates.
| displacement current | A | |
| permittivity of free space | 8.85×10⁻¹² C²/(N·m²) | |
| electric flux | N·m²/C |
A changing electric flux through the surface in question, such as the gap of a charging capacitor.
Only meaningful where an actual changing electric flux exists (e.g. between capacitor plates) — outside such a region there is no displacement current to speak of.
Ampère's law gives inconsistent answers for a charging capacitor depending on which surface bounded by the loop is chosen — one pierced by the wire's current, another passing between the plates where no charge actually flows. Maxwell resolved this by adding a term based on the changing electric flux, which agrees with the real current term outside the capacitor and fills the gap between the plates.
No charge actually flows as displacement current — it is the changing electric FLUX between the plates that produces the same magnetic effect a real current would.