Signals And Systems Set 2

Electrical Engineering

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This set of Signals and Systems Multiple Choice Questions & Answers (MCQs) focuses on Signals And Systems Set 2

Q1 | A signal is a physical quantity which does not vary with                          
  • time
  • space
  • independent variables
  • dependent variables
Answer: dependent variables
Explaination:
a signal is a physical quantity which varies with time, space or any other independent variables. therefore, it does not vary with dependent variables.
Q2 | Most of the signals found in nature are
  • continuous-time and discrete-time
  • continuous-time and digital
  • digital and analog
  • analog and continuous-time
Answer: analog and continuous-time
Explaination:
signals naturally are continuous-time signals. these are also known as analog signals. continuous-time or analog signals are defined for all values of time t.
Q3 | Which one of the following is not a characteristic of a deterministic signal?
  • exhibits no uncertainty
  • instantaneous value can be accurately predicted
  • exhibits uncertainty
  • can be represented by a mathematical equation
Answer: exhibits uncertainty
Explaination:
deterministic signal is one which exhibits no uncertainty and its instantaneous value can be accurately predicted from its mathematical equation. therefore, a deterministic signal doesn’t exhibit uncertainty. however, a random is always uncertain.
Q4 | Sum of two periodic signals is a periodic signal when the ratio of their time periods is
  • a rational number
  • an irrational number
  • a complex number
  • an integer
Answer: a rational number
Explaination:
sum of two periodic signals is a periodic signal only when the ratio of their time periods is a rational number or it is the ratio of two integers. for e.g., t1/t2 = 5/7 → periodic; t1/t2 = 5 → aperiodic.
Q5 | Determine the Time period of: x(t)=3 cos(20t+5)+sin(8t-3).
  • 1/10 sec
  • 1/20 sec
  • 2/5 sec d 2/4 sec
Answer: 2/5 sec d 2/4 sec
Q6 | Determine the odd component of the signal: x(t)=cost+sint.
  • sint
  • 2sint
  • cost
  • 2cost
Answer: cost
Explaination:
here is the explanation.
Q7 | Is the signal sin(t) anti-symmetric?
  • yes
  • no
Answer: yes
Explaination:
a signal is said to be anti- symmetric or odd signal when it satisfies the following condition:
Q8 | For an energy signal                      
  • e=0
  • p= ∞
  • e= ∞
  • p=0
Answer: p=0
Explaination:
a signal is called an energy signal if the energy satisfies 0
Q9 | Determine the power of the signal: x(t) = cos(t).
  • 1/2
  • 1 c) 3/2
  • d) 2
Answer: 1/2
Explaination:
here is the explanation.
Q10 | Is the following signal an energy signal? x(t) = u(t) – u(t – 1)
  • yes
  • no
Answer: yes
Explaination:
here is the explanation.
Q11 | A signal is anti-causal if                              
  • x(t) = 0 for t = 0
  • x(t) = 1 for t < 0
  • x(t) = 1 for t > 0
  • x(t) = 0 for t > 0
Answer: x(t) = 0 for t > 0
Explaination:
a signal is said to be anti- causal when x(t) = 0 for t > 0.
Q12 | Is the signal x(t)= eat u(t) causal?
  • yes
  • no
Answer: yes
Explaination:
a signal is said to be causal if it is 0 for t < 0.
Q13 | Is the signal x(n) = u(n + 4) – u(n – 4) causal?
  • yes
  • no
Answer: no
Explaination:
a signal is said to be causal if it is 0 for t < 0.
Q14 | The type of systems which are characterized by input and the output capable of taking any value in a particular set of values are called as
  • analog
  • discrete
  • digital
  • continuous
Answer: continuous
Explaination:
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
Q15 | An example of a discrete set of information/system is
  • the trajectory of the sun
  • data on a cd
  • universe time scale
  • movement of water through a pipe
Answer: data on a cd
Explaination:
the rest of the parameters are continuous in nature. data is stored in the form of discretized bits on cds.
Q16 | A system which is linear is said to obey the rules of
  • scaling
  • additivity
  • both scaling and additivity
  • homogeneity
Answer: both scaling and additivity
Explaination:
a system is said to be additive and scalable in order to be classified as a linear system.
Q17 | A time invariant system is a system whose output
  • increases with a delay in input
  • decreases with a delay in input
  • remains same with a delay in input
  • vanishes with a delay in input
Answer: remains same with a delay in input
Explaination:
a time invariant system’s output should be directly related to the time of the output. there should be no scaling, i.e. y(t) = f(x(t)).
Q18 | Should real time instruments like oscilloscopes be time invariant?
  • yes
  • sometimes
  • never
  • they have no relation with time variance
Answer: yes
Explaination:
oscilloscopes should be time invariant, i.e they should work the same way everyday, and the output should not change with the time at which it is operated.
Q19 | All real time systems concerned with the concept of causality are
  • non causal
  • causal
  • neither causal nor non causal
  • memoryless
Answer: causal
Explaination:
all real time systems are causal, since they cannot have perception of the future, and only depend on their memory.
Q20 | A system is said to be defined as non causal, when
  • the output at the present depends on the input at an earlier time
  • the output at the present does not depend on the factor of time at all
  • the output at the present depends on the input at the current time
  • the output at the present depends on the input at a time instant in the future
Answer: the output at the present depends on the input at a time instant in the future
Explaination:
a non causal system’s output is said to depend on the input at a time in the future.
Q21 | When we take up design of systems, ideally how do we define the stability of a system?
  • a system is stable, if a bounded input gives a bounded output, for some values of the input
  • a system is unstable, if a bounded input gives a bounded output, for all values of the input
  • a system is stable, if a bounded input gives a bounded output, for all values of the input
  • a system is unstable, if a bounded input gives a bounded output, for some values of the input
Answer: a system is stable, if a bounded input gives a bounded output, for all values of the input
Explaination:
for designing a system, it should be kept in mind that the system does not blow out for a finite input. thus, every finite input should give a finite output.
Q22 | All causal systems must have the component of
  • memory
  • time invariance
  • stability
  • linearity
Answer: memory
Explaination:
causal systems depend on the functional value at an earlier time, compelling the system to possess memory.
Q23 | What are fourier coefficients?
  • the terms that are present in a fourier series
  • the terms that are obtained through fourier series
  • the terms which consist of the fourier series along with their sine or cosine values
  • the terms which are of resemblance to fourier transform in a fourier series are called fourier series coefficients
Answer: the terms which consist of the fourier series along with their sine or cosine values
Explaination:
the terms which consist of the fourier series along with their sine or cosine values are called fourier coefficients. fourier coefficients are present in both exponential and trigonometric fourier series.
Q24 | Which are the fourier coefficients in the following?
  • a0, an and bn
  • an
  • bn
  • an and bn
Answer: a0, an and bn
Explaination:
these are the fourier coefficients in a trigonometric fourier series. a0 = 1/t∫x(t)dt
Q25 | Do exponential fourier series also have fourier coefficients to be evaluated.
  • true
  • false
Answer: true
Explaination:
the fourier coefficient is : xn = 1/t∫x(t)e-njwtdt.
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