BEE BEE Bachelor of Electrical Engineering Electromagnetic Fields and Waves Questions and Answers 2 — Questions and Answers
Question 1: What is the divergence of the magnetic flux density B in free space according to Maxwell's equations?
- Always zero (Correct answer)
- Equal to the magnetic charge density
- Equal to the current density
- Proportional to the electric field
Correct answer: Always zero
Gauss's law for magnetism states that the divergence of B is always zero, confirming that magnetic monopoles do not exist.
Question 2: A uniform plane wave propagates in the +z direction in a lossless medium with relative permittivity 4 and relative permeability 1. What is the phase velocity of the wave?
- 1.5 × 10⁸ m/s (Correct answer)
- 3 × 10⁸ m/s
- 6 × 10⁸ m/s
- 0.75 × 10⁸ m/s
Correct answer: 1.5 × 10⁸ m/s
Phase velocity is c/√(εᵣμᵣ) = 3×10⁸/√4 = 1.5 × 10⁸ m/s.
Question 3: Which boundary condition holds for the tangential component of the electric field at an interface between two perfect dielectrics?
- It is continuous across the boundary (Correct answer)
- It is zero at the boundary
- It is discontinuous by an amount equal to the surface charge
- It doubles at the boundary
Correct answer: It is continuous across the boundary
The tangential component of E is always continuous across the interface between two dielectrics with no surface charges.
Question 4: In a parallel plate capacitor with plate separation d and voltage V, what is the magnitude of the uniform electric field between the plates?
- V/d (Correct answer)
- Vd
- V/d²
- V²/d
Correct answer: V/d
For a parallel plate capacitor, the uniform electric field magnitude is simply E = V/d.
Question 5: What does the Poynting vector represent in electromagnetic theory?
- The direction and magnitude of power flow per unit area (Correct answer)
- The energy stored in the magnetic field
- The rate of charge accumulation on a surface
- The force per unit charge on a test particle
Correct answer: The direction and magnitude of power flow per unit area
The Poynting vector S = E × H gives the instantaneous power flow per unit area in the direction of wave propagation.
Question 6: A 10 GHz electromagnetic wave travels through free space. What is its wavelength?
- 3 cm (Correct answer)
- 30 cm
- 0.3 cm
- 3 m
Correct answer: 3 cm
Wavelength λ = c/f = 3×10⁸/10×10⁹ = 0.03 m = 3 cm.
BEE BEE Bachelor of Electrical Engineering Electromagnetic Fields and Waves Questions and Answers 2
What is the divergence of the magnetic flux density B in free space according to Maxwell's equations?