Explore topic-wise MCQs in Electrical Machines.

This section includes 19 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

In the lab, two students X and Y conducted the experiments to verify the name plate ratings of the transformer.But student X conducted the same at higher frequency. The kVA reading of student X will be ___________

A. higher than Y’s reading
B. lower than Y’s reading
C. same as Y’s reading
D. none of the mentioned
Answer» B. lower than Y’s reading
Discussion
2.

Auto transformer rating is chosen so as to have best performance when the analogous two winding transformer has ___________

A. two voltage levels fairly close to each other
B. very high transformation ratio
C. any voltage levels
D. step down purpose
Answer» B. very high transformation ratio
Discussion
3.

A 200V, 10 hp, 4 poles, 60 Hz, Y-connected induction motor had full load slip of 5%. Then the rotor speed of the motor with respect to stator is?

A. 1710 rpm
B. 1800 rpm
C. 90 rpm
D. 3510 rpm
Answer» B. 1800 rpm
Discussion
4.

For a separately excited dc machine of 25 kW, 250 V and armature resistance of 0.25 ohms, is running at 3000 rpm with supply of 255 V. The electromagnetic power produced at the armature in kilo watts is?

A. 5
B. 10
C. 0.5
D. 8
Answer» B. 10
Discussion
5.

A 3-phase, five limbed shell type transformer, star connected, 200V, 50 Hz, 100 kVA will have ___________

A. no third harmonic current in its phase but has sinusoidal flux
B. third harmonic current in its phase but has flat-topped flux
C. no third harmonic current in its phase but has flat-topped flux
D. third harmonic current in its phase but has sinusoidal flux
Answer» B. third harmonic current in its phase but has flat-topped flux
Discussion
6.

While conducting lab experiments on DC machine loading, the students are given a machine with its rating as 100 kW maximum rating. Then the _____________

A. machine can’t be overloaded after 100 kW
B. machine can be overloaded after 100 kW
C. machine can be overloaded by 5% for a small time duration
D. machine can be overloaded by 10%
Answer» B. machine can be overloaded after 100 kW
Discussion
7.

The desired voltage regulation for a single phase, 50 Hz transformer is zero. Its pu ohmic drop is 4% and pu reactive drop is 4%. The required power factor angle for the operation in degrees is?

A. 45
B. 90
C. 30
D. 60
Answer» B. 90
Discussion
8.

If the dimension of a single phase transformer is made sqrt(3) times less than the original structure, then what is new no load current rating of the transformer?

A. 1/sqrt(3)
B. sqrt(3)
C. 3
D. 1/3*sqrt(3)
Answer» B. sqrt(3)
Discussion
9.

Refer the diagram; a single-phase supply of 100V, 50Hz is fed to the step-up transformer having primary impedance of 1 ohms and secondary impedance 20 ohms. What is the power consumed by the load of 5 ohms?

A. 20 W
B. 40 W
C. 10 W
D. 100 W
Answer» B. 40 W
Discussion
10.

A_200V,_10_HP,_4_POLES,_60_HZ,_Y-CONNECTED_INDUCTION_MOTOR_HAD_FULL_LOAD_SLIP_OF_5%._THEN_THE_ROTOR_SPEED_OF_THE_MOTOR_WITH_RESPECT_TO_STATOR_IS?$

A. 1710 rpm
B. 1800 rpm
C. 90 rpm
D. 3510 rpm
Answer» B. 1800 rpm
Discussion
11.

In the lab, two students X and Y conducted the experiments to verify the name plate ratings of the transformer.But student X conducted the same at higher frequency. The kVA reading of student X will be$

A. higher than Y’s reading
B. lower than Y’s reading
C. same as Y’s reading
D. none of the mentioned
Answer» B. lower than Y‚Äö√Ñ√∂‚àö√ë‚àö¬•s reading
Discussion
12.

Auto_transformer_rating_is_chosen_so_as_to_have_best_performance,_when_the_analogous_two_winding_transformer_has$

A. two voltage levels fairly close to each other
B. very high transformation ratio.
C. any voltage levels
D. step down purpose.
Answer» B. very high transformation ratio.
Discussion
13.

If two alternators A and B are operated in parallel having per unit synchronous reactance as 0.02 ohms and 0.05 ohms respectively.Then what the ratio of contributing loading of machine A to B?

A. 2.5
B. 0.4
C. 1
D. can not be operated in parallel
Answer» B. 0.4
Discussion
14.

For a separately excited dc machine of 25 kW, 250 V and armature resistance of 0.25 ohms, is running at 3000 rpm with supply of 255 V.

A.
B. 5
C. 10
Answer» B. 5
Discussion
15.

A 3-phase, five limbed shell type transformer, star connected, 200V, 50 Hz, 100 kVA will have

A. no third harmonic current in its phase but has sinusoidal flux
B. third harmonic current in its phase but has flat-topped flux
C. no third harmonic current in its phase but has flat-topped flux
D. third harmonic current in its phase but has sinusoidal flux
Answer» B. third harmonic current in its phase but has flat-topped flux
Discussion
16.

While conducting lab experiments on DC machine loading, the students are given a machine with its rating as 100 kW maximum rating. Then

A. machine can’t be overloaded after 100 kW
B. machine can be overloaded after 100 kW
C. machine can be overloaded by 5% for a small time duration
D. machine can be overloaded by 10%
Answer» B. machine can be overloaded after 100 kW
Discussion
17.

The desired voltage regulation for a single phase, 50 Hz transformer is zero. Its pu ohmic drop is 4% and pu reactive drop is 4%. The required power factor angle for the operation in degrees

A. 45
B. 90
C. 30
D. 60
Answer» B. 90
Discussion
18.

For a single phase, 50 Hz transformer, if the open circuit test is conducted at 40 Hz. What is the variation in the no-load power factor of the transformer?

A. Decreases
B. Increases
C. Remains constant
D. None of the mentioned
Answer» B. Increases
Discussion
19.

If the dimension of a single phase transformer is made sqrt(3) times less than the original structure,then what is new no load current rating of the transformer?

A. 1/sqrt(3)
B. sqrt(3)
C. 3
D. 1/3*sqrt(3)
Answer» B. sqrt(3)
Discussion