Exam Questions Papers - Exam Paper 1 (3)

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Exam Questions Papers - Exam Paper 1

17.

A noiseless 3 KHz channel can transmit binary at the rate __________ .

A.	12000 bps
B.	10000 bps
C.	6000 bps
D.	3000 bps

Answer: Option C

Explanation:

Maximum data rate for noiseless channel is given by Nyquist Theorem

= 2H log₂ V bits/sec

V - discrete levels (Here Binary i.e. 2)

H - Bandwidth

∴ Maximum data rate = 2H log₂ V

= 2(3 KHz) log₂ 2 = 2 x 3 x 10³ x 1

= 6 x 10³ = 6000 bps.

18.

The antenna current of an AM transmitter is 8 A, when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by a single sine wave. Determine the antenna current when the percent of modulation changes to 0.8

A.	9.19 A
B.	9.91 A
C.	10.56 A
D.	8.61 A

Answer: Option A

Explanation:

I_c = 8 A

m = 0.8

4-797-73-1

4-797-73-2

= 8 x 1.149 = 9.19 A.

19.

In the circuit below, delay of the EXOR and AND

4-788-45-1

4-788-45-2

Logic gates are 20 μs and 10 μs respectively, then the wave y' and y (with initial condition y = 1) will be :

A.
B.
C.
D.

Answer: Option B

Explanation:

Since y is at logic '1' initially, y' must be at logic '1'.

Also, one input of the EXOR gate is tied to zero therefore 'f' will be directly transferred to the output.

The logic gates will introduce gate delays which will lead to the answer .

20.

If the system T.F. is 2-756-44-1 The differential equation representing the system is

A.
B.
C.
D.	none of these

Answer: Option C

Explanation:

2-764-44-7

(s³ + 2s² + 5s + 6)y(s) = (s² + 4) x (s)

s³y(s) + 2s²y(s) + 5sy(s) + 6y(s) = s² x (s) + 4 x (s)

Replacing s by 2-763-35-1 and y(s) by y(t) and x(s) by x(t) we get

2-764-44-1 y(t) + 2 2-764-44-2 y(t) + 5 2-763-35-1 y(t) + 6y(t)

= 2-764-44-2 x(t) + 4x(t)

2-764-44-5 + 2 2-764-44-3 + 5 2-764-44-6 + 6 = 2-764-44-4 + 4x

21.

The analog signal given below is sampled at 1200 samples per second. m(t) = 2 sin 120 pt + 3 sin 240 pt + 4 sin 360 pt + 5 sin 480 pt + 6 sin 600 pt + 7 sin 720 pt. The folding (maximum) frequency is __________ .

A.	300 Hz
B.	360 Hz
C.	600 Hz
D.	480 Hz

Answer: Option C

Explanation:

Folding frequency (max.) = 4-794-38-1 = 600 Hz.

22.

Consider a unity feedback control system with open-loop transfer function 16-02-22 The steady state error of the system due to a unity step input is :

A.	zero
B.	K
C.	1/K
D.	infinite

Answer: Option A

Explanation:

16-06-22

23.

If x₁[n] 10-02-18 x₁(z) with ROC = R₁ and x₂[n] x₂(z) with ROC = R₂ then ROC for x₁[n] + x₂[n] will be __________ (where R_i → Region of convergence and x₁[n] and x₂[n] are causal).

A.	R1 ∩ R2
B.	R1 ∪ R2
C.	(R1 ∪ R2) ∩ (R1)
D.	(R1 ∩ R2) ∪ (R1)

Answer: Option A

Explanation:

R₁ ∩ R₂, Suppose R₁ for x₁(n) be

10-07-18

Then ROC for x₁(n) + x₂(n)

R₁ ∩ R₂ (R₁ < R₂)

Then ROC for x₁(n) + x₂(n)

R₁ ∩ R₂(R₁ < R₂)

10-07-18-1

24.

During transmission over a communicate channel, bit errors occur independently with probability 16-227-2 . If a block of 3 bits are transmitted, the probability of at most one bit error is equal to