Practice question

**Charging capacitor** conduction current in wires equals displacement current between plates because dQ/dt = I_c = ε₀ A dE/dt = ε₀ dΦ_E/dt = I_d, preserving charge conservation, magnetic field between plates due to I_d, same as that due to conduction current. Gauss's Law for electricity states that the electric flux through a closed surface is proportional to the charge enclosed, given by oint E · d A = (Q/ε₀) . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields oint E · d A = (Q/ε₀), illustrating EM wave transverse nature and Maxwell's displacement current concept.