Signals & Systems Questions and Answers – Properties of LTI Systems – 1

This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Properties of LTI Systems – 1”.

1. What is the rule h*(x+y) = (y+x)*h called?
a) Commutativity rule
b) Associativity rule
c) Distributive rule
d) Transitive rule
View Answer

Answer: a
Explanation: By definition, the commutative rule h*x=x*h.

2. Does the system h(t) = exp([-1-2j]t) correspond to a stable system?
a) Yes
b) No
c) Marginally Stable
d) None of the mentioned
View Answer

Answer: c
Explanation: The system corresponds to an oscillatory system, this resolving to a marginally stable system.

3. What is the rule h*(x*c) = (x*h)*c called?
a) Commutativity rule
b) Associativity rule
c) Distributive rule
d) Associativity and Commutativity rule
View Answer

Answer: d
Explanation: By definition, the commutative rule i h*x=x*h and associativity rule = h*(x*c) = (h*x)*c.
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4. Is y[n] = n*cos(n*pi/4)u[n] a stable system?
a) Yes
b) No
c) Marginally stable
d) None of the mentioned
View Answer

Answer: b
Explanation: The ‘n’ term in the y[n] will dominate as it reaches to infinity, and hence could reach infinite values.

5. What is the rule (h*x)*c = h*(x*c) called?
a) Commutativity rule
b) Associativity rule
c) Distributive rule
d) Transitive rule
View Answer

Answer: b
Explanation: By definition, the associativity rule = h*(x*c) = (h*x)*c.

4. Is y[n] = n*sin(n*pi/4)u[-n] a stable system?
a) Yes
b) No
c) Marginally stable
d) None of the mentioned
View Answer

Answer: b
Explanation: The ‘n’ term in the y[n] will dominate as it reaches to negative infinity, and hence could reach infinite values. Eventhough + infinity would not be a problem, still the resultant system would be unstable.

7. What is the following expression equal to: h*(c*(b+d(t))), d(t) is the delta function
a) h*c + h*b
b) h*c*b + b
c) h*c*b + h*c
d) h*c*b + h
View Answer

Answer: c
Explanation: Apply commutative and associative rules
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8. Does the system h(t) = exp([1-4j]t) correspond to a stable system?
a) Yes
b) No
c) Marginally Stable
d) None of the mentioned
View Answer

Answer: b
Explanation: The system corresponds to an unstable system, as the Re(exp) term is a positive quantity.

9. The system transfer function and the input if exchanged will still give the same response.
a) True
b) False
View Answer

Answer: a
Explanation: By definition, the commutative rule i h*x=x*h=y. Thus, the response will be the same.
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10. For an LTI discrete system to be stable, the square sum of the impulse response should be
a) Integral multiple of 2pi
b) Infinity
c) Finite
d) Zero
View Answer

Answer: c
Explanation: If the square sum is infinite, the system is an unstable system. If it is zero, it means h(t) = 0 for all t. However, this cannot be possible. Thus, it has to be finite.

Sanfoundry Global Education & Learning Series – Signals & Systems.

To practice all areas of Signals & Systems, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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