Braking of DC Motor MCQ [Free PDF] – Objective Question Answer for Braking of DC Motor Quiz

91. The length of phasor is ___________

A. R.M.S
B. Average
C. Peak to Peak
D. Minimum

Answer: A

Phasors are the rotating values that rotate with some angular frequency Ω. The length of the phasor value is r.m.s value.   

 

92. Transient analysis is only applicable to bounded systems.
A. True
B. False

Answer: A

Bounded systems are those systems that have some finite maximum value and are decaying functions. Transient analysis is only applicable to bounded signals as they achieve a steady-state after some time.   

 

93. Calculate the velocity of the ball if the angular speed is 7 rad/s and the radius is .2 m.

A. 2.5 m/s
B. 1.4 m/s
C. 4.5 m/s
D. 1.0 m/s

Answer: B

The velocity of the ball can be calculated using the relation V=Ω×r. The velocity is the vector product of angular speed and radius.

V = Ω×r = 7×.2 = 1.4 m/s.   

 

94. Calculate the value of the time period if the frequency of the signal is .001 Hz.

A. 1000 sec
B. 2000 sec
C. 5000 sec
D. 1500 sec

Answer: A

The time period is defined as the time after the signal repeats itself. It is expressed in second.

T = 1÷F=1÷.001=1000 sec.   

 

95. Calculate the value of the frequency of the 440 V DC supply.

A. 100 Hz
B. 0 Hz
C. 200 Hz
D. 500 Hz

Answer: B

The frequency is defined as the number of oscillations per second. It is reciprocal to the time period. DC supply magnitude is constant. It does not change with time so the frequency of DC supply is 0 Hz.   

 

96. Calculate the value of the power factor if the values of R and Z are 2 Ω and 10 Ω.

A. 0.8
B. 0.5
C. 0.2
D. 0.4

Answer: C

The power factor is defined as the ratio of active power to apparent power.

Cos(φ)=R÷Z=2÷10=.2.

It has no unit.   

 

97. Calculate the value of capacitor voltage during resonance condition if the value of supply voltage is 20 V and the quality factor is 3.

A. 60 V
B. 50 V
C. 10 V
D. 30 V

Answer: A

During the resonance condition XL=Xc.

The value of the capacitor voltage is Q×Vs.

The power factor of the circuit is one.

Vc=20×3=60 V.   

 

98. When 30 A current flows into the positive terminal of current source 8 V. Calculate the power delivered by the source.

A. -240 W
B. 360 W
C. -430 W
D. 500 W

Answer: A

When the current enters the positive terminal of an element it will always absorb the power and when the current leaves the positive terminal it will deliver the power.

Power delivered is -30×8=-240 W.   

 

99. The slope of the V-I curve is 17.587o. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

A. .322 Ω
B. .360 Ω
C. .316 Ω
D. .778 Ω

Answer: C

The slope of the V-I curve is resistance. The slope given is 17.587o so

R=tan(17.587o)=.316 Ω.

The slope of the I-V curve is reciprocal to resistance.   

 

100. Calculate the equivalent inductance when two inductors are connected in parallel of values 12 H and 12 H.

A. 6 H
B. 10 H
C. 12 H
D. 8 H

Answer: A

When two inductors are connected in parallel their equivalent inductance is equal to the harmonic mean of the inductances.

Leq=L1×L2÷(L1+L2)=6 H.   

 

101. Calculate the active power in an 0 Ω resistor with 0 current flowing through it.

A. inf MW
B. 0 MW
C. 2 MW
D. 18 MW

Answer: B

The resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in the case of the resistor so the angle between V & I is 0o.

P=I2R=0×0×0=0 MW.   

 

102. When 1 A current flows out of the positive terminal of voltage source 6 V. Calculate the power delivered by the source.

A. 6 W
B. 7 W
C. -9 W
D. -5 W

Answer: A

When the current enters the positive terminal of an element it will always absorb the power and when the current leaves the positive terminal it will deliver the power. Power delivered by the source is

1×6=6 W.   

 

103. Calculate the value of inductor voltage during resonance condition if the value of supply voltage is 7 V and the quality factor is 9.

A. 59 V
B. 63 V
C. 73 V
D. 33 V

Answer: B

During the resonance condition XL=Xc. The value of the inductor voltage is Q×Vs. The power factor of the circuit is one.

Vc=7×9=63 V.   

 

104. A circuit consists of a 3 F capacitor and a 5 H inductor. Determine the order of the circuit.

A. 2
B. 1
C. 3
D. 0

Answer: A

The order of the circuit is the number of memory/storing elements that are non-separable present in the circuit. In mathematics, the order is defined as the highest order derivate in the differential equation. The order of the circuit is 2.   

 

105. The forced response is due to a source present in the circuit.

A. True
B. False

Answer: A

The steady-state response is a part of the forced response. The forced response is due to the electrical source present in the circuit. Its mathematical equation involves the source present in the circuit.   

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106. Full form of DTC.

A. Direct torque control
B. Digital torque control
C. Discrete torque control
D. Distribution torque control

Answer: A

DTC stands for Direct torque control. DTC and IFOC are the techniques used for controlling the speed and torque of a 3-phase induction motor.   

 

107. The characteristic shown by an element in the I-V curve is V=I2. The nature of the element is _______

A. Non-linear, Bilateral, Passive
B. Linear, Unilateral, Active
C. Linear, Bilateral, Passive
D. Non-linear, Unilateral, Active

Answer: D

The nature of the element is non-linear, unilateral, and active. The shape of the characteristic is parabolic. For bilateral nature, it should be symmetrical in the first and third quadrants. Its slope is negative in the second quadrant which determines its active nature.   

 

108. Transient response is a temporary response.

A. True
B. False

Answer: A

Transient response is a primary response in the circuit. It is a temporary response that dies out at t=infinity. It consists of exponential decaying functions.   

 

109. Calculate the steady-state value for x(t)=4(1-e-3t).

A. 5
B. 4
C. 3
D. 2

Answer: B

The steady-state value is obtained at t=∞.

The value of x(t) at t=∞ is

4(1-e-∞)=4(1-0)=4.

The term e-3t is an exponentially decaying function.   

 

110. The natural response is due to _________ conditions present in the circuit.

A. Initial
B. Final
C. Zero
D. Negative

Answer: A

The natural response is due to the initial conditions present in the circuit. The natural response is a complete part of the transient response. It is mathematically represented as y(t)=yo×e-at.   

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