Practice question

**Ampere-Maxwell law** ∮ B·dl = μ₀(I_c + ε₀ dΦ_E/dt) generalizes Ampere's law, displacement current arises from time-varying electric field, source of magnetic field like conduction current. For rate of change of flux 2×10¹¹ V·m/s, I_d = ε₀×2×10¹¹ =8.85×10⁻¹²×2×10¹¹=1.77 A. The speed of electromagnetic waves in vacuum depends only on the permittivity ( ε₀ ) and permeability ( μ₀ ) of free space, given by c = (1/√(μ₀ ε₀)) , which is constant. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Dependence on permittivity and permeability, illustrating EM wave transverse nature and Maxwell's displacement current concept.