# Practice Questions on Electromagnetics

 Q1. The electric field component of a time harmonic plane EM wave traveling in a nonmagnetic lossless dielectric medium has an amplitude of 1 V/m.  If the relative permittivity of the medium is 4, the magnitude of the time-average power density vector (in W/$\text m^2$) is:
 A. $\dfrac{1}{30\pi}$ B. $\dfrac{1}{60\pi}$ C. $\dfrac{1}{120\pi}$ D. $\dfrac{1}{240\pi}$

 Q2. The inner broad-wall dimension of a rectangular waveguide having $\text{TE}_{10}$ mode as dominant mode is 2.5 cm. The cut off frequency for the mode $\text{TE}_{30}$ is:
 A. 9 GHz B. 18 GHz C. 22 GHz D. 34 GHz

 Q3. A current sheet in the +z direction, $K=8 a_{z}\text A/\text m$ at $x=0$ separates region 1, $x<0$ where $H_{1}=12a_{y} \text A/m$ and region 2 $x>0$. The value of $H$ (in $\text A/m$) in region 2 at $x=+0$.
 A. $8a_{y}$ B. $14a_{y}$ C. $16a_{x}$ D. $20a_{y}$

 Q4. The propagation constant of a lossy dielectric medium is 0.0183 rad/s and has a loss tangent 0.2. The dielectric constant of the medium 2.5. The carrier frequency of the signal propagating in this medium is:
 A. 340 kHz B. 550 kHz C. 790 kHz D. 1120 kHz

 Q5. The electric field of a uniform plane wave is given by \begin{align*} E&=\hat {x}30\sin (3\pi 10^8-\pi z)+\hat y 30 \cos (3\pi 10^8t-\pi z)\text{ V/m} \end{align*} The corresponding magnetic field is:
 A. $-\hat x 0.079\cos (3\pi 10^8t-\pi z)+\hat y 0.079\sin (3\pi 10^8 t-\pi z)\text{ A/m}$ B. $-\hat x 0.054\cos (3\pi 10^8t-\pi z)-\hat y 0.054\sin (3\pi 10^8 t-\pi z)\text{ A/m}$ C. $-\hat x 0.079\cos (3\pi 10^8t-\pi z)+\hat y 0.054\sin (3\pi 10^8 t-\pi z)\text{ A/m}$ D. $-\hat x 0.054\cos (3\pi 10^8t-\pi z)-\hat y 0.079\sin (3\pi 10^8 t-\pi z)\text{ A/m}$

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