Electronics and Communication Engineering - Exam Questions Papers

46. 

The order of the differential equation
is

A. 1
B. 2
C. 3
D. 4

Answer: Option B

Explanation:

The order of differential equation is two.


47. 

A radio wave is incident on a layer of ionosphere at an angle of 30° with the vertical. If the critical frequency is, 1.2 MHz, the maximum usable frequency is

A. 1.2 MHz
B. 2.4 MHz
C. 0.6 MHz
D. 1.386 MHz

Answer: Option D

Explanation:

fmuf = for sec i = 1.2 x 106 x sec (30°) = 1.386 MHz.


48. 

The Thevenin resistance of the circuit is

A.
B.
C. 3 K
D.

Answer: Option D

Explanation:

Diode is the non-linear element

Find RTH across diode short voltage supplies.

RAB= RTH = 3K + (2K || 1K)

.


49. 

Fourier transform of signal obtained after taking difference between step function and its reverse version is given as __________ .

A. 2jω
B. 2/jω
C. 4/jω
D. 4jω

Answer: Option B

Explanation:

u(t) - u(-t) = sgn (t)


50. 

An air-filled rectangular waveguide has dimensions 8cm x 10cm . The group velocity is

A. 1.8 x 108 m/s
B. 2.6 x 108 m/s
C. 3 x 108 m/s
D. 0.3 x 108 m/s

Answer: Option B

Explanation:

=2.6 x 108 m/s.


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