Explore topic-wise MCQs in Electrical Engineering.

This section includes 76 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.

1.

A rotary converter combines the function of

A. an induction motor and a D.C. generator
B. a synchronous motor and a D.C. generator
C. a D.
D. none of the above
Answer» C. a D.
Discussion
2.

The efficiency of the copper oxide rectifier seldom exceeds

A. 90 to 95%
B. 85 to 90%
C. 80 to 85%
D. 65 to 75%
Answer» E.
Discussion
3.

Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply?

A. Mechanical rectifiers
B. Copper oxide rectifiers
C. Selenium rectifiers
D. Electrolytic rectifiers
Answer» E.
Discussion
4.

In a rotary converter I2R losses as compared to a D.C. generator of the same size will be

A. same
B. less
C. double
D. three times
Answer» C. double
Discussion
5.

Which of the following mercury arc rectifier will deliver least undulating current?

A. Six-phase
B. Three-phase
C. Two-phase
D. Single-phase
Answer» B. Three-phase
Discussion
6.

In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.

A. accelerates
B. decelerates
C. any of the above
D. none of the above
Answer» B. decelerates
Discussion
7.

A rotary converter is a single machine with

A. one armature and one field
B. two armatures and one field
C. one armature and two fields
D. none of the above
Answer» B. two armatures and one field
Discussion
8.

The efficiency of an electrolytic rectifier is nearly

A. 80%
B. 70%
C. 60%
D. 40%
Answer» D. 40%
Discussion
9.

A rotary converter operates at a

A. low power factor
B. high power factor
C. zero power factor
D. none of the above
Answer» C. zero power factor
Discussion
10.

Which of the following is reversible in action?

A. Motor generator set
B. Motor converter
C. Rotary converter
D. Any of the above
E. None of the above
Answer» D. Any of the above
Discussion
11.

Selenium rectifier can be operated at temperatures as high as

A. 25°C
B. 40°C
C. 60°C
D. 75°C
Answer» E.
Discussion
12.

Which of the following is the loss within the mercury arc rectifier chamber?

A. Voltage drop in arc
B. Voltage drop at the anode
C. Voltage drop at the cathode
D. All of the above
Answer» E.
Discussion
13.

Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required?

A. Motor-generator set
B. Motor converter
C. Rotary converter
D. Mercury arc rectifier
Answer» E.
Discussion
14.

It is the_______of the transformer on which the magnitude of angle of overlap depends.

A. resistance
B. capacitance
C. leakage reactance
D. any of the above
Answer» D. any of the above
Discussion
15.

Mercury, in arc rectifiers, is chosen for cathode because

A. Its ionization potential is relatively low
B. Its atomic weight is quite high
C. Its boiling point and specific heat are low
D. All of the above
Answer» E.
Discussion
16.

A rotary converter operates at a%!

A. low power factor
B. high power factor
C. zero power factor
D. none of the above
Answer» C. zero power factor
Discussion
17.

Which of the following is reversible in action?%!

A. Motor generator set
B. Motor converter
C. Rotary converter
D. Any of the above
E. None of the above
Answer» D. Any of the above
Discussion
18.

Selenium rectifier can be operated at temperatures as high as%!

A. 25°C
B. 40°C
C. 60°C
D. 75°C
Answer» E.
Discussion
19.

Which of the following is the loss within the mercury arc rectifier chamber?%!

A. Voltage drop in arc
B. Voltage drop at the anode
C. Voltage drop at the cathode
D. All of the above
Answer» E.
Discussion
20.

*$_Which of the following is the loss within the mercury arc rectifier chamber??

A. Voltage drop in arc
B. Voltage drop at the anode
C. Voltage drop at the cathode
D. All of the above
Answer» E.
Discussion
21.

*$_Which of the following mercury arc rectifier will deliver least undulating current??

A. Six-phase
B. Three-phase
C. Two-phase
D. Single-phase
Answer» B. Three-phase
Discussion
22.

*$_A rotary converter combines the function of?

A. an induction motor and a D.C. generator
B. a synchronous motor and a D.C. generator
C. a D.
D. none of the above
Answer» C. a D.
Discussion
23.

*/*_Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required??

A. Motor-generator set
B. Motor converter
C. Rotary converter
D. Mercury arc rectifier
Answer» E.
Discussion
24.

%_Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required?_%

A. Motor-generator set
B. Motor converter
C. Rotary converter
D. Mercury arc rectifier
Answer» E.
Discussion
25.

_ In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.$?

A. accelerates
B. decelerates
C. any of the above
D. none of the above
Answer» B. decelerates
Discussion
26.

_ The efficiency of the copper oxide rectifier seldom exceeds$?

A. 90 to 95%
B. 85 to 90%
C. 80 to 85%
D. 65 to 75%
Answer» E.
Discussion
27.

__It is the_______of the transformer on which the magnitude of angle of overlap depends.__

A. resistance
B. capacitance
C. leakage reactance
D. any of the above
Answer» D. any of the above
Discussion
28.

_A rotary converter is a single machine with$?

A. one armature and one field
B. two armatures and one field
C. one armature and two fields
D. none of the above
Answer» B. two armatures and one field
Discussion
29.

_Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply?$?

A. Mechanical rectifiers
B. Copper oxide rectifiers
C. Selenium rectifiers
D. Electrolytic rectifiers
Answer» E.
Discussion
30.

Mercury, in arc rectifiers, is chosen for cathode because$?

A. Its ionization potential is relatively low
B. Its atomic weight is quite high
C. Its boiling point and specific heat are low
D. All of the above
Answer» E.
Discussion
31.

Mercury, in arc rectifiers, is chosen for cathode because?

A. Its ionization potential is relatively low
B. Its atomic weight is quite high
C. Its boiling point and specific heat are low
D. All of the above
Answer» E.
Discussion
32.

The efficiency of an electrolytic rectifier is nearly?

A. 80%
B. 70%
C. 60%
D. 40%
Answer» D. 40%
Discussion
33.

In a rotary converter I2R losses as compared to a D.C. generator of the same size will be?

A. same
B. less
C. double
D. three times
Answer» C. double
Discussion
34.

In which of the following equipment direct current is needed?

A. Telephones
B. Relays
C. Time switches
D. All of the above
Answer» E.
Discussion
35.

The voltage drop at anode, in a mercury arc rectifier is due to

A. self restoring property of mercury
B. high ionization potential
C. energy spent in overcoming the electrostatic field
D. high temperature inside the rectifier
Answer» D. high temperature inside the rectifier
Discussion
36.

Ageing of a selenium rectifier may change the output voltage by

A. 5 to 10 per cent
B. 15 to 20 per cent
C. 25 to 30 per cent
D. none of the above
Answer» B. 15 to 20 per cent
Discussion
37.

In a three-phase mercury arc rectifiers each anode conducts for

A. One-third of a cycle
B. One-fourth of a cycle
C. One-half a cycle
D. Two-third of a cycle
Answer» B. One-fourth of a cycle
Discussion
38.

A commutating rectifier consists of commutator driven by

A. An induction motor
B. A synchronous motor
C. A D.C. series motor
D. A D.C. shunt motor
Answer» C. A D.C. series motor
Discussion
39.

In a mercury arc rectifier characteristic blue luminosity is due to

A. colour of mercury
B. ionization
C. high temperature
D. electron streams
Answer» C. high temperature
Discussion
40.

In a mercury arc rectifier______ flow from anode to cathode

A. ions
B. electrons
C. ions and electrons
D. any of the above
Answer» B. electrons
Discussion
41.

The ionization potential of mercury is approximately

A. 5.4 V
B. 8.4 V
C. 10.4 V
D. 16.4 V
Answer» D. 16.4 V
Discussion
42.

Which of the following rectifiers have been used extensively in supplying direct current for electroplating?

A. Copper oxide rectifiers
B. Selenium rectifiers
C. Mercury arc rectifiers
D. Mechanical rectifiers
E. None of the above
Answer» C. Mercury arc rectifiers
Discussion
43.

With a motor converter it is possible to obtain D.C. voltage only upto

A. 200-100 V
B. 600-800 V
C. 1000-1200 V
D. 1700-2000 V
Answer» E.
Discussion
44.

The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?

A. They are mechanically strong
B. They do not require any voltage for filament heating
C. Both (A) and (B)
D. None of the above
Answer» D. None of the above
Discussion
45.

In a rotary converter armature currents are

A. d.c. only
B. a.c. only
C. partly a.c. and partly d.c.
D. none of the above
Answer» D. none of the above
Discussion
46.

A mercury arc rectifier possesses ________ regulation characteristics

A. straight line
B. curved line
C. exponential
D. none of the above
Answer» E.
Discussion
47.

In a single phase rotary converter the number of slip rings will be

A. two
B. three
C. four
D. six
Answer» B. three
Discussion
48.

On which of the following factors the number of phases for which a rectifier should be designed depends?

A. The voltage regulation of the rectifier should be low
B. In the output circuit there should be no harmonics
C. The power factor of the system should be high
D. All of the above
Answer» E.
Discussion
49.

The applications of selenium rectifiers are usually limited to potential of

A. 10 V
B. 30 V
C. 60 V
D. 100 V
E. 200 V
Answer» E. 200 V
Discussion
50.

The cathdde voltage drop, in a mercury arc rectifier, is due to

A. expenditure of energy in ionization
B. surface resistance
C. expenditure of energy in overcoming the electrostatic field
D. expenditure of energy in liberating electrons from the mercury
Answer» E.
Discussion