Signals & Systems – MCQs

1. : A signal that is defined for all time is called a:
(A) Discrete-time signal
(B) Continuous-time signal
(C) Periodic signal
(D) Non-periodic signal

2. : The unit step function u(t) is defined as:
(A) 0 for t < 0, 1 for t ≥ 0
(B) 1 for t < 0, 0 for t ≥ 0
(C) 0 for all t
(D) 1 for all t

3. : A system is said to be linear if it satisfies:
(A) Stability and causality
(B) Homogeneity and additivity
(C) Time-invariance
(D) Memoryless behavior

4. : What is the convolution of two signals used for?
(A) To subtract signals
(B) To determine system response
(C) To add signals
(D) To determine signal symmetry

5. : A periodic signal satisfies the condition:
(A) x(t) = x(t + T)
(B) x(t) = x(-t)
(C) x(t) = 0
(D) x(t) = 1

6. : The Dirac delta function δ(t) is defined as:
(A) ∞ at t = 1
(B) ∞ at t = 0, with ∫ δ(t) dt = 1
(C) 0 at t = 0
(D) Constant for all t

7. : A system is time-invariant if its behavior:
(A) Changes over time
(B) Is the same regardless of time shift
(C) Depends on memory
(D) Requires feedback

8. : The Laplace Transform is useful for:
(A) Time domain analysis
(B) Frequency domain analysis
(C) Voltage measurement
(D) Digital signal generation

9. : The Fourier Series is used to represent:
(A) Non-periodic signals
(B) Periodic signals
(C) Discrete signals only
(D) Complex functions

10. : Which of the following is an energy signal?
(A) Unit step signal
(B) Sinusoidal signal
(C) Gaussian pulse
(D) Ramp signal

11. : An LTI system stands for:
(A) Linear Time-Dependent
(B) Linear Time-Independent
(C) Linear Time-Invariant
(D) Logarithmic Transfer Integration

12. : The z-transform is applied to:
(A) Continuous signals
(B) Analog filters
(C) Discrete-time signals
(D) Time-invariant systems only

13. : The Fourier Transform of a δ(t) is:
(A) 1
(B) 0
(C) ∞
(D) e^(-jωt)

14. : A system is causal if:
(A) Output depends only on past and present inputs
(B) Output depends on future inputs
(C) Output is independent of input
(D) Input is delayed

15. : The frequency domain representation of a signal provides information about its:
(A) Amplitude
(B) Phase
(C) Frequency content
(D) All of the above

16. : Stability of a system means:
(A) Output is zero
(B) Output is unbounded
(C) Bounded input leads to bounded output
(D) System has feedback

17. : What is the output of an LTI system with input δ(t)?
(A) Step function
(B) Impulse response
(C) Zero
(D) Sinusoidal function

18. : The convolution of any signal with δ(t) yields:
(A) Zero
(B) The derivative of the signal
(C) The original signal
(D) The integral of the signal

19. : What is the effect of time-scaling a signal x(t) to x(2t)?
(A) Compresses the signal
(B) Expands the signal
(C) Delays the signal
(D) Advances the signal

20. : Even signals satisfy the condition:
(A) x(t) = -x(t)
(B) x(t) = x(-t)
(C) x(t) = 0
(D) x(t) = 1

21. : The Laplace transform of e^(-at)u(t) is:
(A) 1/s
(B) s/(s+a)
(C) 1/(s+a)
(D) a/s

22. : The Nyquist rate is:
(A) Equal to signal frequency
(B) Half the sampling rate
(C) Twice the highest frequency of the signal
(D) Always 1 Hz

23. : A band-limited signal contains frequencies up to:
(A) Infinite
(B) Certain maximum value
(C) Zero
(D) 1 Hz

24. : Which operation in time domain corresponds to multiplication in frequency domain?
(A) Convolution
(B) Addition
(C) Time scaling
(D) Differentiation

25. : A memoryless system is one where the output at any time depends only on:
(A) Future input
(B) Past input
(C) Present input
(D) No input