# 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. ∞

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

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

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)

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

Explanation:

β = ωLC = 106 x 2p x 500 x  