Electromagnetic Fields and Waves Flashcards

Which of the following correctly states Faraday's Law of electromagnetic induction in differential form?

Answer: ∇ × E = -∂B/∂t

Faraday's Law states that the curl of E equals the negative time rate of change of B.

A parallel-plate capacitor with plate area A and separation d is filled with a dielectric of permittivity ε. What is the electric field inside if voltage V is applied?

Answer: V/d

The electric field between parallel plates is E = V/d, independent of the dielectric permittivity for a given voltage.

What is the skin depth δ for a good conductor with conductivity σ, permeability μ, at frequency f?

Answer: Both A and B are equivalent

Both 1/√(πfμσ) and √(2/ωμσ) are equivalent expressions for skin depth since ω = 2πf.

The Poynting vector S = E × H represents which physical quantity?

Answer: Power density flowing through a surface

The Poynting vector gives the instantaneous power per unit area (W/m²) transported by an EM wave.

For a uniform plane wave in free space, the ratio of the magnitudes |E|/|H| equals:

Answer: Both A and B since 377 ≈ 120π

The intrinsic impedance of free space η₀ = √(μ₀/ε₀) ≈ 377 Ω = 120π Ω.

Gauss's Law for magnetism (∇ · B = 0) physically implies:

Answer: Magnetic monopoles do not exist

Zero divergence of B means magnetic field lines always form closed loops, confirming no isolated magnetic charges (monopoles) exist.

Which condition must the tangential components of E satisfy at an interface between two lossless dielectrics?

Answer: E₁t = E₂t (continuous)

Tangential electric field components must be continuous across any dielectric–dielectric boundary.