Electronics and Communication Engineering - Exam Questions Papers

Exercise : Exam Questions Papers - Exam Paper 7

31.

A transmitted using AM has in modulated carrier output power of 10 KW and can be modulated to a maximum depth of 90% by a sinusoidal modulating voltage without causing overloading. Find the value to which an modulated carrier power can be increased without resulting in overloading if the maximum permitted modulating index is 40%

14 KW

12.96 KW

26.96 KW

2.96 KW

Answer: Option

Explanation:

Now P_T is fixed, μ = 0.4

Then P_C is P_C =

32.

The signal flow graph of a system is shown in figure. The transfer function of the system is :

Answer: Option

Explanation:

P₁ = 1 [Path R(s to C(s)]

Δ = 1 - (L₁ - L₂ + L₃) + L₁L₂

P₁ = 1; Δ₁ = 1

[Non touching loop gain to forward path]

33.

The Laplace transform of the given waveform is

(1 - e^-s + e^-2s)

(1 - 2e^-s + e^-2s)

(1 - 2e^-s)

Answer: Option

Explanation:

f(t) = f₁(t) + f₂(t) + f₃(t)

= 2tu(t) - 2 x 2(t - 1) + 2(t - 2)u(t - 2)

f(s) = - e^-s + e^-2s

= (1 - 2e^-s + e^-2s).

34.

With respect to the following 555 timer circuit what will be the value of R_A and R such that the LED turns on for a duration of 10 ms every time it receives negative trigger pulse. LED operating current = 20 mA, V_f = 1.4 V, Vo _on = 13.4 V and C = 0.22 nf

41.4 KΩ, 600 Ω

45 KΩ, 630 Ω

43.5 KΩ, 580 Ω

44.9 KΩ, 600 Ω

Answer: Option

Explanation:

Timer operated in mono, mode

R_AC =

∴ R_A = 41.4 KΩ

R = = 600 Ω.

35.

The region between a pin of parallel perfectly conducting planes of infinite extent is y and z directions is partially filled with a dielectric as shown below.