Displacement current (Ampère–Maxwell) (I_d = ε₀ dΦ_E/dt)

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I_d = ε₀ dΦ_E/dt

What each symbol means

SymbolWhat it stands for
I_dDisplacement current through a surface (A)
Φ_EElectric flux through that surface (N·m²/C)
ε₀Permittivity of free space

When to use this

Defined so total current (conduction + displacement) is continuous; essential in capacitor charging and EM wave propagation.