Find the noise factor for an antenna at 27�C with equivalent noise temperature 3

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Question
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

Correct Answer

1.1

Explanation

T_e = T₀(F - 1)

Find the noise factor for an antenna at 27�C with equivalent noise temperature 30�K 20 100 300 1.1 T .

Electromagnetic Field Theory problems

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1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. The torque (in mm) acting on a circular current loop of radius 1 mm in the xy plane, connected at the origin and with current 0.1 A, flowing in the sense of increasing in a magnetic field
is
Options
A.
B.
C. 10^-12p
D. - 10^-12p

10. Calculate the wave impedance for TM mode in rectangular waveguide for dominant mode at 3 GHz having
Options
A. (120p) ?
B. 377 ?
C. 226 ?
D. 629 ?

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