DC Series Motors MCQ Questions & Answers

DC Series Motors MCQs : This section focuses on the "DC Series Motors". These Multiple Choice Questions (MCQs) should be practiced to improve the DC Series Motors skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

At the starting, the field is very strong but it decreases with time because of the ________

A. Reduction in armature current
B. Increase in armature current
C. Reduction in speed
D. Increase in speed

Question 2

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

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

Question 3

Calculate the current in DC series field winding using the following data: Ia=3 A.

A. 4 A
B. 2 A
C. 3 A
D. 6 A

Question 4

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

Question 5

Calculate the flux produced by the DC series field winding using the following data: Ia=5 A, N=23, R=23.

A. 5 Wb
B. 6 Wb
C. 9 Wb
D. 8 Wb

Question 6

Calculate the time period of the waveform x(t)=1cot(?t+7?).

A. 0.5 sec
B. 1 sec
C. 3 sec
D. 5 sec

Question 7

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

Question 8

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

Question 9

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

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

Question 10

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

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

Question 11

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

Question 12

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

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

Question 13

DC series motors are used where the high ________ torque is required.

A. Maximum
B. Minimum
C. Starting
D. Stalling

Question 14

Dynamic braking requires a strong _________

A. Magnetic field
B. Electrostatic field
C. Nuclear field
D. Gravitational field

Question 15

For a given torque, increasing diverter resistance of a DC series motor causes the ________

A. decrease in speed and less armature current
B. decrease in speed but armature current remains the same
C. increase in speed and more armature current
D. increase in speed but armature current remains the same

Question 16

For faster braking, the series field is separated from the armature circuit.

A. True
B. False

Question 17

In DC series machine ? is directly proportional to Ia.

A. True
B. False

Question 18

In dynamic braking, DC series motor behaves as a ____________

A. Separately excited motor
B. Transformer
C. Induction motor
D. Thyristor

Question 19

Instantaneous power in the 3-? system is constant.

A. True
B. False

Question 20

The field diverter resistance for a DC series motor is kept ________

A. High
B. Low
C. zero
D. one

Question 21

The length of phasor is ___________

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

Question 22

The shape of the current-torque current characteristics in DC series motor is a __________

A. Rectangular Hyperbolic
B. Parabola
C. Circle
D. Ellipse

Question 23

The shape of the speed-armature current characteristics in DC series motor are __________

A. Hyperbolic
B. Parabola
C. Circle
D. Ellipse

Question 24

The shape of the speed-torque current characteristics in DC series motor are __________

A. Rectangular Hyperbolic
B. Parabola
C. Circle
D. Ellipse

Question 25

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 ?
B. .360 ?
C. .316 ?
D. .778 ?

Question 26

What is the condition for maximum power transfer theorem in DC circuits?

A. RL=2Rth
B. RL?Rth
C. RL?Rth
D. RL=Rth

Question 27

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

Question 28

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

Question 29

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

Question 30

Calculate the current in DC series field winding using the following data: Ia=3 A.

A. 4:00 AM
B. 2:00 AM
C. 3:00 AM
D. 6:00 AM

Question 31

Calculate the time period of the waveform x(t)=1cot(πt+7π).

A. 0.5 sec
B. 1 sec
C. 3 sec
D. 5 sec

Question 32

Calculate the value of 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

Question 33

In DC series machine ∅ is directly proportional to Ia.

A. TRUE
B. FALSE

Question 34

Instantaneous power in the 3-φ system is constant.

A. TRUE
B. FALSE

Question 35

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