Electronics and Communication Engineering - Exam Questions Papers

46. 

If the closed-loop transfer function T(s) of a unity negative feedback system is given by then the steady state error for a unit ramp input is :

A.
B.
C.
D.

Answer: Option D

Explanation:

.


47. 

In 8085 microprocessor system, can an input and output port have same port address?

A. Yes
B. No
C. Insufficient data
D. None of these

Answer: Option A

Explanation:

Since microprocessor differentiates between an input or output operation on a port depending upon control signals RD and WR .

Therefore in a microprocessor system same port address can be given to two different input and output ports.


48. 

5 skilled workers can build a wall in 20 days; 8 semi-skilled worker can build a wall in 25days; 10 unskilled workers can build a wall in 30 days, If a team has 2 killed, 6 semi-skilled and 5 unskilled workers, how long will it take to build the wall?

A. 20 days
B. 18 days
C. 16 days
D. 15 days

Answer: Option D

Explanation:

Given, 5 skilled workers can build a wall in 20 days i.e., 1 skilled worker can the wall build in 100 days

The capacity of each skilled worker is

8 semi-skilled workers can build a wall in 25 days i.e., 1 semi-skilled worker can build a wall in 200 days

The capacity of each semi-skilled worker is

Similarly, The capacity of 1 unskilled worker is

Now, The capacity of 2 skilled + 6 semi-skilled + 5 unskilled workers is

The required numbers of days is 15.


49. 

The fourier transform of the half cosine pulse as shown below is __________

A. 0.5 {sin [0.5(f - 1)] + sin [0.5 (f + 1)]}
B. 0.25 [sin c[0.25 (f - 2)1 + sin c[0.25(f + 2)]]
C. 0.5 {sin c [0.5 (f - 1)] + sin c [0.5 (f + 1)]}
D. sin c(f - 0.5) + sin c (f + 0.5)

Answer: Option C

Explanation:

The given signal can be expressed as multiplication of x1(t) and x2(t) as shown below, where A = 2, T/2 = 0.25 ⇒ T = 0.5

x(t) = x1(t) x x2(t)

⇒ X(f) = X1(f) * X2(f)

Now X1(f) = [δ(f - f0) + δ(f + f0)]

where

and X2(f) = T . sin c[fT]

⇒ X(f) = [δ(f - f0) + δ(f + f0)]

*T. sinc(fT)

= [sinc[T(f - f0)] + sinc [T(f + f0)]]

Now, A = 2, T = 0.5

and

⇒ X(f) = 0.5[sin c(0.5(f - 1)) + sinc(0.5(f + 1))].


50. 

A lossless transmission line is 50 cm long and operates at a frequency of 500 MHz. Inductance and capacitances present in a line are 0.5 μH/m and 200 pF/m. Phase constant and phase velocity are respectively.

A. 5p, 2p x 108 m/sec
B. 5p, 108 m/sec
C. 31.4, 108 m/sec
D. 31.4, 2p x 108 m/sec

Answer: Option B

Explanation:

β = ωLC = 106 x 2p x 500 x


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