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Electromagnetic Field Theory problems

2. In a 100 turn coil, if the flux through each turn is (t³ - 2t)mW_b, the magnitude of the induced emf in the coil at a time of 4 sec is
Options
A. 46 mV
B. 56 mV
C. 4.6 V
D. 5.6 V

3. Charge needed within a unit sphere centred at the origin for producing a potential field,
Options
A. 12 p_c
B. 60 p_c
C. 120 p_c
D. 180 p_c

4. A wave is propagated in a waveguide at frequency of 9 GHz and separation is 2 cm between walls Calculate group velocity for dominant mode.
Options
A. 1.8 x 10⁸ m/sec
B. 5 x 10⁸ m/sec
C. 3 x 10⁸ m/sec
D. 1.5 x 10⁸ m/sec

5. A hollow rectangular waveguide has dimensions a = 2b. Calculate the amount of attenuation, if the frequency is 3 GHz, and b = 1 cm.
Options
A. 49
B. 47.33
C. 50.33
D. 50

6. A plane electromagnetic wave travels in dielectric medium of relative permittivity 9. Relative to free space, the velocity of propagation in the dielectric is
Options
A. increased by a factor of 9
B. increased by a factor of 3
C. unchanged
D. reduced by a factor of 1/3

7. Find the noise factor for an antenna at 27�C with equivalent noise temperature 30�K
Options
A. 20
B. 100
C. 300
D. 1.1

8. Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 10¹⁴ Hz in glass. Assume velocity of light is 3 x 10⁸ m/sec in vacuum.
Options
A. 4 ?m
B. 3 ?m
C. 2 ?m
D. 1 ?m

9. A short circuited stub is shunt connected to a transmission line as shown in the figure is, if z₀ = 500 ohms, the admittance y seen at the function of the stub and the transmission line is
Options
A. (0.01 - j 0.02) mho
B. (0.02 - j 0.01) mho
C. (0.04 - j 0.02) mho
D. (0.02 + j 0) mho

10. Which of the following should dominant wave have?
Options
A. Lowest cut off frequency
B. Highest cut off frequency
C. No attenuation
D. No phase shift

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