BEE Electromagnetic Fields and Waves 3

Question 1

A TEM wave travels in the +z direction with E in the x-direction. The magnetic field H points in which direction?

Accepted Answer

+y direction

Answer

For a +z-propagating wave with E in x̂, H = (1/η)(ẑ × E) points in the +ŷ direction.

Question 2

The displacement current density introduced by Maxwell is given by:

Accepted Answer

∂D/∂t

Answer

Maxwell added the displacement current density Jd = ∂D/∂t to Ampere's law to make it consistent with charge conservation.

Question 3

For a rectangular waveguide, the cutoff frequency of the TE₁₀ mode with broad-wall dimension a is:

Accepted Answer

c/(2a)

Answer

The cutoff frequency for TE₁₀ is fc = c/(2a), making it the dominant (lowest cutoff) mode.

Question 4

The electric potential V due to a point charge Q at distance r in free space is:

Accepted Answer

Q/(4πε₀r)

Answer

The scalar electric potential falls off as 1/r while the electric field falls off as 1/r².

Question 5

Standing waves are formed in a transmission line when:

Accepted Answer

The load is mismatched, causing reflections

Answer

A mismatched load causes partial or total reflection; the incident and reflected waves superpose to form standing waves.

BEE - Bachelor of Electrical Engineering Practice Test