Multiple choice question for engineering
Set 1
1. Consider the loop transfer function K(s+6)/(s+3)(s+5) In the root locus diagram the centroid will be located at:
a) -4
b) -1
c) -2
d) -3
Answer
Answer: c [Reason:] Centroid =Sum of real part of open loop pole-sum of real part of open loop zeros/P-Z.
2. Which one of the following applications software’s is used to obtain an accurate root locus for?
a) LISP
b) MATLAB
c) dBase
d) Oracle
Answer
Answer: b [Reason:] MATLAB stands for mathematics laboratory in which the input is in the form of the matrix and is the best software for drawing root locus.
3. Which one of the following is not the property of root loci?
a) The root locus is symmetrical about imaginary axis
b) They start from the open loop poles and terminate at the open loop zeroes
c) The breakaway points are determined from dK/ds = 0
d) Segments of the real axis are the part of the root locus if and only is the total number of real poles and zeroes to their right is odd.
Answer
Answer: a [Reason:] The root locus is the locus traced due to the gain of the system with changing frequency and need not be symmetrical about origin.
4. The breakaway point calculated mathematically must always lie on the root locus.
a) True
b) False
Answer
Answer: a [Reason:] The breakaway point of the two branches of the root locus is the point where the two branches either meet or they break and may or may not always lie on the root locus.
5. What is the number of the root locus segments which do not terminate on zeroes?
a) The number of poles
b) The number of zeroes
c) The difference between the number of poles and zeroes
d) The sum of the number of poles and the number of the zeroes
Answer
Answer: c [Reason:] The number of the root locus segments which do not lie on the root locus is the difference between the number of the poles and zeroes.
6. Which one of the following are correct?
The root locus is the path of the roots of the characteristic equation traced out in the s-plane?
a) As the input of the system is changed
b) As the output of the system is changed
c) As a system parameter is changed
d) As the sensitivity is changed
Answer
Answer: c [Reason:] The root locus is the locus of the change of the system parameters of the characteristic equation traced out in the s-plane.
7. If the gain of the system is reduced to a zero value, the roots of the system in the s-plane,
a) Coincide with zero
b) Move away from zero
c) Move away from poles
d) Coincide with the poles
Answer
Answer: d [Reason:] The roots of the system in s plane coincides with the poles if the gain of the system is reduced to a value zero.
8. The addition of open loop zero pulls the root loci towards:
a) The left and therefore system becomes more stable
b) The right and therefore system becomes unstable
c) Imaginary axis and therefore system becomes marginally stable
d) The left and therefore system becomes unstable
Answer
Answer: a [Reason:] The system can become stable by reducing the damping and also by adding zeroes in the s plane and moving left of the s plane system becomes more stable.
9. If root loci plots of a particular control system do not intersect the imaginary axis at any point, then the gain margin of the system will be:
a) 0
b) 0.707
c) 1
d) Infinite
Answer
Answer: d [Reason:] The gain margin is the inverse of the intersection of the root loci plot to the imaginary axis and if it does not intersect then the gain margin will be infinite.
10. When the number of poles is equal to the number of zeroes, how many branches of root locus tends towards infinity?
a) 1
b) 2
c) 0
d) Equal to number of zeroes
Answer
Answer: c [Reason:] Branches of the root locus is equal to the number of poles or zeroes which ever is greater and tends toward infinity when poles or zeroes are unequal.
Set 2
1. Routh Hurwitz criterion gives:
a) Number of roots in the right half of the s-plane
b) Value of the roots
c) Number of roots in the left half of the s-plane
d) Number of roots in the top half of the s-plane
Answer
Answer: a [Reason:] Routh Hurwitz criterion gives number of roots in the right half of the s-plane.
2. Routh Hurwitz criterion cannot be applied when the characteristic equation of the system containing coefficient’s which is/are
a) Exponential function of s
b) Sinusoidal function of s
c) Complex
d) Exponential and sinusoidal function of s and complex
Answer
Answer: d [Reason:] Routh Hurwitz criterion cannot be applied when the characteristic equation of the system containing coefficient/s which is/are exponential, sinusoidal and complex function of s.
3. Consider the following statement regarding Routh Hurwitz criterion:
a) It gives absolute stability
b) It gives gain and phase margin
c) It gives the number of roots lying in RHS of the s-plane
d) It gives gain, phase margin and number of roots lying in RHS of the s-plane
Answer
Answer: d [Reason:] Routh Hurwitz gives the absolute stability and roots on the right of the s plane.
4. The order of the auxiliary polynomial is always:
a) Even
b) Odd
c) May be even or odd
d) None of the mentioned
Answer
Answer: a [Reason:] Auxiliary polynomial denotes the derivative of the odd equation which is always even.
5. Which of the test signals are best utilized by the stability analysis.
a) Impulse
b) Step
c) Ramp
d) Parabolic
Answer
Answer: a [Reason:] Computational task is reduced to much extent.
6. The characteristic equation of a system is given as3s4+10s3+5s2+2=0. This system is :
a) Stable
b) Marginally stable
c) Unstable
d) Linear
Answer
Answer: c [Reason:] There is a missing coefficient so the system is unstable.
7. The characteristic equation of a system is given ass3+25s2+10s+50=0. What is the number of the roots in the right half s-plane and the imaginary axis respectively?
a) 1,1
b) 0,0
c) 2,1
d) 1,2
Answer
Answer: b [Reason:] The characteristic equation has no sign changes so number of roots on the right half of s plane is zero.
8. Consider the following statement:
a) A system is said to be stable if its output is bounded for any input
b) A system is said to be stable if all the roots of the characteristic equation lie on the left half of the s plane.
c) A system is said to be stable if all the roots of the characteristic equation have negative real parts.
d) A second order system is always stable for finite values of open loop gain
Answer
Answer: a [Reason:] A system is stable if its output is bounded for bounded input.
9. The necessary condition for the stability of the linear system is that all the coefficients of characteristic equation 1+G(s)H(s) =0, be real and have the :
a) Positive sign
b) Negative sign
c) Same sign
d) Both positive and negative
Answer
Answer: c [Reason:] The necessary condition for the stability of the linear system is that all the coefficients of characteristic equation 1+G(s)H(s) =0, is they must have same sign.
10. For making an unstable system stable:
a) Gain of the system should be increased
b) Gain of the system should be decreased
c) The number of zeroes to the loop transfer function should be increased
d) The number of poles to the loop transfer function should be increased
Answer
Answer: b [Reason:] For making an unstable system stable gain of the system should be decreased.
Set 3
1. A signal flow graph is the graphical representation of the relationships between the variables of set linear algebraic equations.
a) True
b) False
Answer
Answer: a [Reason:] By definition signal flow graphs are the graphical representation of the relationships between the variables of set linear algebraic equations.
2. A node having only outgoing branches.
a) Input node
b) Output node
c) Incoming node
d) Outgoing node
Answer
Answer: a [Reason:] Nodes are the point by which the branches are outgoing or ingoing and this can be input or output node and input node is the node having only outgoing branches.
3. Use mason’s gain formula to find the transfer function of the given signal flow graph:
a) abd/1-(ac)
b) abdeg/1-(bc+ef)+bcef
c) abd/1-(bc+ef)+bcef
d) adcdef/1-(bc+ef)+bcef
Answer
Answer: b [Reason:] Using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops.
4. Use mason’s gain formula to find the transfer function of the following signal flow graph:
a) abcd+efg/1-cd-fg-cdfg
b) acdfg+bcefg/1-cd-fg-cdfg
c) abef+bcd/1-cd-fg-cdfg
d) adcdefg/1-cd-fg-cdfg
Answer
Answer: b [Reason:] Using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops.
5. Loop which do not possess any common node are said to be ___________ loops.
a) Forward gain
b) Touching loops
c) Non touching loops
d) Feedback gain
Answer
Answer: c [Reason:] Loop is the part of the network in which the branch starts from the node and comes back to the same node and non touching loop must not have any node in common.
6. Signal flow graphs:
a) They apply to linear systems
b) The equation obtained may or may not be in the form of cause or effect
c) Arrows are not important in the graph
d) They cannot be converted back to block diagram
Answer
Answer: a [Reason:] Signal flow graphs are used to find the transfer function of control system by converting the block diagrams into signal flow graphs or directly but cannot be used for nonlinear systems.
7. Signal flow graphs are reliable to find transfer function than block diagram reduction technique.
a) True
b) False
Answer
Answer: a [Reason:] As one set technique and formula is used here but in block diagram technique various methods are involved which increases complexity.
8. The relationship between an input and output variable of a signal flow graph is given by the net gain between the input and output node is known as the overall______________
a) Overall gain of the system
b) Stability
c) Bandwidth
d) Speed
Answer
Answer: a [Reason:] The relationship between input and output variable of a signal flow graph is the overall gain of the system.
9. Use mason’s gain formula to calculate the transfer function of given figure:
a) G1/1+G2H
b) G1+G2/1+G1H
c) G2/1+G1H
d) None of the mentioned
Answer
Answer: b [Reason:] Use mason’s gain formula to solve the signal flow graph and by using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops.
10. Use mason’s gain formula to find the transfer function of the given figure:
a) G1+G2
b) G1+G1/1-G1H+G2H
c) G1+G2/1+G1H+G2H
d) G1-G2
Answer
Answer: c [Reason:] Using mason’s gain formula transfer function from signal flow graph can be calculated which relates the forward path gain to the various paths and loops.
Set 4
1. Sampling can be done by:
a) Impulse train sampling
b) Natural sampling
c) Flat-top sampling
d) All of the mentioned
Answer
Answer: d [Reason:] Sampling is the process in which the continuous systems are sampled by the application of the zero order hold and can be done by all the three methods.
2. The first step required to convert analog signal to digital is :
a) Sampling
b) Holding
c) Reconstruction
d) Quantization
Answer
Answer: a [Reason:] Sampling is the process in which the continuous systems are sampled by the application of the zero order hold and is the first step in the conversion of analog to digital signals.
3. Sampling is necessary :
a) In complex control systems
b) Where high accuracy is required
c) Non automated control systems
d) Automated control system
Answer
Answer: b [Reason:] Sampling is the process where the continuous systems are converted into discrete time systems with the help of zero order hold of the signal and sampling is necessary where high accuracy is needed.
4. Sampled data technique is appropriate as:
a) For long distance data transmission
b) Pulses are transferred by little loss of accuracy
c) More than one channel of information is sequentially sampled and transmitted.
d) All of the mentioned
Answer
Answer: d [Reason:] Sampled data technique refers to the data which is sampled and is appropriate as for long distance communication, for accurate transmission and multi channel transmission.
5. Signal sampling reduces the power demand made on the signal.
a) True
b) False
Answer
Answer: a [Reason:] Signal sampling refers to the sampling of the signal and reduces the power demand that is the power required by the signal and is therefore helpful for signals of weak origin.
6. The use of sampled data control system are:
a) For using analog components as the part of the control loop
b) For time division of control components
c) Whenever a transmission channel forms a part of closed loop
d) None of the mentioned
Answer
Answer: c [Reason:] Sampled data control system is the system where the data used is sampled and is used whenever a transmission channel forms a part of closed loop system.
7. _______________ is a sampling pattern which is repeated periodically
a) Single order sampling
b) Multi order sampling
c) Zero order sampling
d) Unordered sampling
Answer
Answer: b [Reason:] Multi-order sampling is a sampling pattern in which the sampling is of different signals and which is repeated periodically.
8. For the successful reconstruction of signals :
a) Sampling frequency must be equal to the message signal
b) Sampling frequency must be greater to the message signal
c) Sampling frequency must be less to the message signal
d) Sampling frequency must be greater than or equal to the message signal
Answer
Answer: d [Reason:] Reconstruction of signals refers to the conversion of the discrete time signals into continuous tiem signals and for the succesful reconstruction of signals sampling frequency must be greater than or equal to the message signal but ideally it is always preferred to be greater.
9. The signal is reconstructed back with the help of
a) Zero order hold circuits
b) Extrapolations
c) Signal is reconstructed with zero order holds and extrapolations
d) Signal is not reconstructed
Answer
Answer: c [Reason:] The signal is reconstructed that is the process of converting the discrete time signals into the continuous time signals and this can be done with the help of hold circuits or extrapolations.
10. Aliasing is caused when:
a) Sampling frequency must be equal to the message signal
b) Sampling frequency must be greater to the message signal
c) Sampling frequency must be less to the message signal
d) Sampling frequency must be greater than or equal to the message signal
Answer
Answer: c [Reason:] Aliasing refers to the process when the discrete time signal is recontructed back then due to the error some part of the signal is lost and is caused when sampling frequency must be less than frequency of message signal.
Set 5
1. Which of the following is an electromechanical device ?
a) Induction relay
b) Thermocouple
c) LVDT
d) Any of the mentioned
Answer
Answer: c [Reason:] LVDT is linear variable differential transformer which is an inductive transducer and converts the displacement of the core to the electrical energy and also is electromechanical device.
2. A differentiator is usually not a part of a control system because it
a) Reduces damping
b) Reduces the gain margin
c) Increases input noise
d) Increases error
Answer
Answer: c [Reason:] A differentiator is the phase lead compensator which increases the speed of response and bandwidth and manages the transient response of the system.
3. If the gain of the critical damped system is increased it will behave as
a) Oscillatory
b) Critically damped
c) Overdamped
d) Underdamped
Answer
Answer: d [Reason:] Gain of the critical system is inversely proportional to the root of the damping factor and hence on increasing the gain the damping reduces and system becomes the underdamped.
4. In a control system integral error compensation _______ steady state error
a) Increases
b) Minimizes
c) Does not have any effect on
d) All of the mentioned
Answer
Answer: b [Reason:] Integral error compensation is the phase lag compensation and reduces the steady state error and eliminates the error.
5. With feedback _____ reduces.
a) System stability
b) System gain
c) System stability and gain
d) None of the mentioned
Answer
Answer: b [Reason:] Feedback reduces the gain as it causes the stability to the closed loop system and for the good control system the stability of the system should be high and also the speed of response.
6. An amplidyne can give which of the following characteristics?
a) Constant current
b) Constant voltage
c) Constant current as well as constant voltage
d) Constant current, constant voltage and constant power
Answer
Answer: d [Reason:] An amplidyne has constant current, voltage and power.
7. Which of the following can be measured by LVDT?
a) Displacement
b) Velocity
c) Acceleration
d) All of the mentioned
Answer
Answer: d [Reason:] LVDT can measure displacement, velocity and acceleration which is a linear variable differential transformer and inductive transducer.
8. ____________directly converts temperature into voltage.
a) Thermocouple
b) Potentiometer
c) Gear train
d) LVDT
Answer
Answer: a [Reason:] Thermocouple is a device that converts the change in the temperature into voltage in which the change in temperature of the different metals results in change in voltage.
9. The transfer function technique is considered as inadequate under which of the following conditions?
a) Systems having complexities and non-linearity’s
b) Systems having stability problems
c) Systems having multiple input disturbances
d) All of the mentioned
Answer
Answer: d [Reason:] Transfer function is the ratio of laplace output to the laplace input with the zero initial conditions and is considered inadequate due to complexity, stability problems and multiple input disturbances.
10. Which of the following is the output of a thermocouple?
a) Alternating current
b) Direct current
c) A.C. voltage
d) D.C. voltage
Answer
Answer: d [Reason:] Thermocouple is the device that is used to convert the change in temperature gives output in DC form.
