BEE Engineering Electromagnetics Fundamentals 2

Question 1

What is the divergence of the magnetic flux density B in free space?

Accepted Answer

∇·B = 0

Answer

Maxwell's equation states that magnetic monopoles do not exist, so the divergence of B is always zero.

Question 2

The capacitance per unit length of a coaxial cable with inner radius a and outer radius b, filled with dielectric ε, is:

Accepted Answer

2πε / ln(b/a)

Answer

Applying Gauss's law to the coaxial geometry yields C/L = 2πε / ln(b/a).

Question 3

In a good conductor, the skin depth δ is related to frequency f and conductivity σ as:

Accepted Answer

δ = √(2/ωμσ)

Answer

Skin depth is defined as δ = √(2/ωμσ), where ω = 2πf, showing fields decay exponentially into the conductor.

Question 4

The Biot-Savart law gives the magnetic field contribution dH from a current element Idl as:

Accepted Answer

dH = (Idl × R̂) / (4πR²)

Answer

The Biot-Savart law states dH = (Idl × R̂)/(4πR²), giving field direction via the cross product.

Question 5

What boundary condition applies to the tangential component of E at the interface between two dielectrics?

Accepted Answer

E_t1 = E_t2

Answer

The tangential component of E is continuous across any dielectric interface (no surface current).

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