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. Using λ = (c/v) , for 7.5 MHz , λ = (3 × 10⁸/7.5 × 10⁶) = 40 m . For 12 MHz , λ = (3 × 10⁸/12 × 10⁶) = 25 m . So the range is 25 m to 40 m . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 25 m