# Power and Energy Signals MCQ’s

This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Power and Energy Signals”.

1. The property of Fourier Transform which states that the compression in time domain is equivalent to the expansion in the frequency domain is ____________
a) Duality
b) Scaling
c) Time scaling
d) Frequency shifting

2. The impulse response h[n] of a linear time-invariant system is h[n] = u [n+3] + u [n-2] – 2u [n-7] where, u[n] is the step unit response. The above system is ________________
a) Stable but not causal
b) Stable and causal
c) Causal but unstable
d) Unstable and not causal

3. For any given signal, average power in its 6 harmonic components as 10 mW each and fundamental component also has 10 mV power. Then, average power in the periodic signal is _______________
a) 70
b) 60
c) 10
d) 5

4. The final value of X(s) = 12(s+1)s(s2+4) is _________
a) 1
b) 2
c) 3
d) Undetermined

5. Given that, F(s) = ws2+w2. Re[s]>0. The final value of f(t) is ___________
a) 0
b) 1
c) [-1,1]
d) ∞

6. A band-limited signal with a maximum frequency of 5 kHz is to be sampled. According to the sampling theorem, the sampling frequency which is not valid is _______________
a) 5 kHz
b) 12 kHz
c) 15 kHz
d) 20 kHz

7. The Laplace transform of a signal is given as Y(s) = 1s(s−1), then the final value is ___________
a) -1
b) 0
c) 1
d) Unbounded

8. A voltage LT is given as 4s2+3s+27s2+6s+5. It is applied across a 2H inductor having zero initial current. The current in the inductor at t = ∞ is ___________
a) 0
b) 1/5 A
c) 2/7 A
d) 2/5 A

9. A current I given by I = – 8 + 62–√ (sin (ωt + 30°)) A is passed through three meters. The respective readings (in ampere) will be?
a) 8, 6 and 10
b) 8, 6 and 8
c) – 8, 10 and 10
d) -8, 2 and 2

10. Given that X(s) is the Laplace transform of the signal cos 2t u (t). The time signal corresponding to (s+1) X(s) is _________________
a) (cos 2t – 2 sin 2t) u (t)
b) (cos 2t + sin2t2) u (t)
c) (cos 2t + 2 sin 2t) u (t)
d) (cos 2t – sin2t2) u (t)

11. Increased pulse-width in the flat-top sampling , leads to ______________
a) Attenuation of high frequencies in reproduction
b) Attenuation of low frequencies in reproduction
c) Greater aliasing errors in reproduction
d) No harmful effects in reproduction

12. Given, R = 10 Ω, L = 100 mH and C = 10 μF. Selectivity is ____________

a) 10
b) 1.2
c) 0.15
d) 0.1

13. Let x(t) be a continuous time, real valued signal band limited to F Hz. The Nyquist sampling rate in Hz, for y(t) = x(0.5t) + x(t) – x(2t) is ______________
a) F
b) 2F
c) 4F
d) 8F

14. A relay coil having voltage of magnitude 210 V and frequency 50 Hz is connected to a 210 V, 50 Hz supply. If it has resistance of 50 Ω and an inductance of 0.2 H, the apparent power is _____________
a) 549.39 VA
b) 275.6 VA
c) 157 VA
d) 187 VA

15. A band pass signal extends from 4-6 kHz. The smallest sampling frequency required to attain all the information in the signal is _________________
a) 10 kHz
b) 8 kHz
c) 6 kHz
d) 4 kHz