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Electronics and Communication Engineering - Exam Questions Papers

Exercise : Exam Questions Papers - Exam Paper 11
36.
A system with transfer function H(z) has impulse response h(.) defined as h(2) = 1, h(3) = -1 and h(k) = 0 otherwise. Consider the following statements
S1: H(z) is a low pass filter
S2: H(z) is a FIR filter.
Which of the following is correct?
Only S2 is true
Both S1 and S2 are false
Both S1 and S2 are true, and S2 is a reason for S1
Both S1 and S2 are true, but S2 is not a reason for S1
Answer: Option
Explanation:

H(ejω) = e-j2ω - e-j3ω. It is FIR high pass filter

37.
Consider an incremental vector element of length ΔL and angle between an electric field E and ΔL s cos θ.

Then in which direction should ΔL be placed to be obtain maximum value of Δv?
In the direction of E
In opposite direction of E
In the angle of 45° with E
In the angle of 60° with E
Answer: Option
Explanation:

Now E is a definite value at the point which it is present and is independent of direction of ΔL.

The magnitude of ΔL is constant and direction is along the unit vector.

∴ Maximum value of Δv will occur at cos θ = - 1 or ΔL points in opposite direction to E.

38.
A MOD - 2 counter, the FF has a tpd = 60 nsec. The NOR gate has a tpd of 30 nsec. The clock frequency is
37 MHz
40 MHz
111 MHz
none
Answer: Option
Explanation:

Clock period should be greater than or equal tpd

MOD-12 → X FF = 4 x 60 = 240 n sec

tpd of NOR gate = 30 n sec Total = 240 + 30 ⇒ 270 n sec

.

39.
Evaluate the power stored in inductor and capacitor
25 J, 12.5 J
12.5 J, 25 J
25 J, 50 J
12.5 J, 50 J
Answer: Option
Explanation:

Energy stored in inductor L is

as inductor will act as a short circuit for dc.

∴ EL

Energy stored in capacitor C is

Voltage across capacitor C is 5 V (i.e. voltage across shunt resistor R)

∴ EC

40.
If the Laplace transform of the voltage transform of the voltage across a capacitor of value F is the value of the current through the capacitor at t = 0+ is
0 A
2 A
A
1 A
Answer: Option
Explanation:

capacitor =

∴ I(s) = vc(s)/c(s)

.

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