Electromagnetic Fields and Waves Flashcards

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

Answer: +y direction

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

The displacement current density introduced by Maxwell is given by:

Answer: ∂D/∂t

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

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

Answer: c/(2a)

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

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

Answer: Q/(4πε₀r)

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

Standing waves are formed in a transmission line when:

Answer: The load is mismatched, causing reflections

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

The attenuation constant α for a lossy dielectric medium is primarily associated with:

Answer: Power absorption (heat loss) per unit length

α (Np/m) describes the exponential decay of wave amplitude due to energy absorption in the medium.

Brewster's angle is defined as the angle of incidence at which:

Answer: No reflected wave exists for parallel (p) polarization

At Brewster's angle, the reflection coefficient for p-polarization (TM) is zero, so only s-polarization reflects.