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ECE : Signals and Systems - Quiz(MCQ)
A)
the output at the present depends on the input at the current time
B)
the output at the present depends on the input at an earlier time
C)
the output at the present does not depend on the factor of time at all
D)
the output at the present depends on the input at a time instant in the future

Correct Answer : Option (D) :   the output at the present depends on the input at a time instant in the future


Explanation : A non causal system’s output is said to depend on the input at a time in the future.

A)
causal
B)
non causal
C)
memoryless
D)
neither causal nor non causal

Correct Answer : Option (A) :   causal


Explanation : All real time systems are causal, since they cannot have perception of the future, and only depend on their memory.

A)
analog
B)
discrete
C)
digital
D)
continuous

Correct Answer : Option (B) :   discrete


Explanation : Discrete systems have their input and output values restricted to enter some quantised/discretized levels.

A)
y(n) = x(n)
B)
y(n) + y(n - 1)
C)
y(n) + y(n - 1) + y(n + 1)
D)
y(n) + y(n - 1) + y(n + 3) = 0

Correct Answer : Option (C) :   y(n) + y(n - 1) + y(n + 1)


Explanation : Because present output of y(n) depend upon past y(n - 1) and future y(n + 1).

A)
10
B)
20
C)
50
D)
100

Correct Answer : Option (D) :   100


Explanation :

Energy density spectrum = |G(f)|2 = |10|2 = 100.

6 .
A voltage V(t) is a Gaussian ergodic random process with a mean of zero and a variance of 4 volt2. If it is measured by a dc meter. The reading will be
A)
B)
2
C)
4
D)
√2

Correct Answer : Option (A) :   0

7 .
A first order system will never be able to give a __________ response

1. band stop
2. band pass
3. all pass

Choose the correct option
A)
1, 2, 3 true
B)
1, 2 are true 3 is false
C)
1 and 3 true, 2 false
D)
1, 2 are false, 3 is true

Correct Answer : Option (B) :   1, 2 are true 3 is false


Explaination : Because to design band pass or band stop, transfer function of must be second order.

8 .
The z-transform of a particular signal is given



The system after implementation will be
A)
casual and stable
B)
casual and unstable
C)
non-casual and stable
D)
non-casual and unstable

Correct Answer : Option (A) :   casual and stable


Explaination :

Include unity circle and exterior of circle hence x(z) will be stable, causal.

9 .
If transfer function of a system is H(z) = 6 + z-1 + z-2 then system is
A)
mixed phase
B)
maximum phase
C)
minimun phase
D)
None of the above

Correct Answer : Option (C) :   minimun phase


Explaination :

H(z) = 6 + z-1 - z-2, solve it by considering H(z) = 0 z = 1/3, -1/2 in H(z) only numerator.

Hence z = 1/3, - 1/2 will be zero, and if zero lies inside the unit circle, system will be of minimum phase.

A)
digital
B)
analog
C)
discrete
D)
continuous

Correct Answer : Option (D) :   continuous


Explanation : Continuous systems have a restriction on the basis of the upper bound and lower bound, but within this set, the input and output can assume any value. Thus, there are infinite values attainable in this system