Explore topic-wise MCQs in Electrical Engineering Questions.

This section includes 57 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.

1.

Which of the following AC. motors is usually used in large motor-generator sets?
A. Synchronous motor
B. Squirrel cage induction motor
C. Slip ring induction motor
D. Any of the above
Answer» B. Squirrel cage induction motor
Discussion
2.

A synchronous converter can be started______________?
A. by means of a small auxiliary motor
B. from AC. side as induction motor
C. from D.C. side as D.C. motor
D. any of the above methods
E. none of the above methods
Answer» E. none of the above methods
Discussion
3.

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
4.

Which of the following are the applications of D.C. system ?
A. Battery charging work
B. Arc welding
C. Electrolytic and electro-chemical processes
D. Arc lamps for search lights
E. All of the above
Answer» F.
Discussion
5.

Which of the following methods may be used to convert A.C. system to D.C ?
A. Rectifiers
B. Motor converters
C. Motor-generator sets
D. Rotary converters
E. All of the above
Answer» F.
Discussion
6.

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.C. series motor and a D.C. generator
D. none of the above
Answer» C. a D.C. series motor and a D.C. generator
Discussion
7.

In a single phase rotary converter the number of slip rings will be_____________?
A. two
B. three
C. four
D. six
E. none
Answer» B. three
Discussion
8.

In a glass bulb mercury arc rectifier the maximum current rating is restricted to___________?
A. 2000 A
B. 1500 A
C. 1000 A
D. 500 A
Answer» E.
Discussion
9.

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
10.

The internal efficiency of a mercury arc rectifier depends on___________?
A. voltage only
B. current only
C. voltage and current
D. r.m.s. value of current
E. none of the above
Answer» B. current only
Discussion
11.

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
12.

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
13.

When a rectifier is loaded which of the following voltage drops take place ?
A. Voltage drop in transformer reactance
B. Voltage drop in resistance of transformer and smoothing chokes
C. Arc voltage drop
D. All of the above
Answer» E.
Discussion
14.

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
15.

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
16.

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
17.

A mercury arc rectifier possesses __________ regulation characteristics
A. straight line
B. curved line
C. exponential
D. none of the above
Answer» E.
Discussion
18.

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
19.

Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of _____________?
A. 100 A at 100 V
B. 200 A at 200 V
C. 300 A at 300 V
D. 400 A at 400 V
E. 500 A at 500 V
Answer» F.
Discussion
20.

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
21.

To produce cathode spot in a mercury arc rectifier______________?
A. anode is heated
B. tube is evacuated
C. an auxiliary electrode is used
D. low mercury vapour pressures are used
Answer» D. low mercury vapour pressures are used
Discussion
22.

The advantage of mercury arc rectifier is that________________?
A. it is light in weight and occupies small floor space
B. it has high efficiency
C. it has high overload capacity
D. it is comparatively noiseless
E. all of the above
Answer» F.
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.

In a mercury pool rectifier, the voltage drop across its electrodes___________?
A. is directly proportional to load
B. is inversely proportional to load
C. varies exponentially with the load current
D. is almost independent of load current
Answer» E.
Discussion
25.

If cathode and anode connections in a mercury arc rectifier are inter changed_____________?
A. the rectifier will not operate
B. internal losses will be reduced
C. both ion and electron streams will move in the same direction
D. the rectifier will operate at reduced efficiency
Answer» B. internal losses will be reduced
Discussion
26.

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
27.

In which of the following appUcations, direct current is absolutely essential ?
A. Illumination
B. Electrolysis
C. Variable speed operation
D. Traction
Answer» C. Variable speed operation
Discussion
28.

The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following_____________?
A. anode drop and cathode drop
B. anode drop and arc drop
C. cathode drop and arc drop
D. anode drop, cathode drop and arc drop
Answer» E.
Discussion
29.

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
30.

In a rotary converter armature currents are______________?
A. d.c. only
B. a.c. only
C. partly a.c. and partly d.c.
Answer» D.
Discussion
31.

The potential drop in the arc, in a mercury arc rectifier, varies_____________?
A. 0.05 V to 0.2 V per cm length of the arc
B. 0.5 V to 1.5 V per cm length of the arc
C. 2 V to 3.5 V per cm length of the arc
D. none of the above
Answer» D. none of the above
Discussion
32.

In a mercury arc rectifier positive ions are attracted towards______________?
A. anode
B. cathode
C. shell bottom
D. mercury pool
Answer» C. shell bottom
Discussion
33.

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
34.

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
35.

On which of the following factors the number of phases for which a rectifier should be designed depend ?
A. The voltage regulation of the rec¬tifier should be low
B. In the output circuit there should be no harmonics
C. The power factor of the system should be high
D. The rectifier supply transformer should be utilized to the best ad-vantage
E. all of the above
Answer» F.
Discussion
36.

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
37.

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. it remains in liquid state at ordi¬nary temperature
E. all of the above
Answer» F.
Discussion
38.

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
39.

Which of the following metals is generally manufactured by electrolysis process ?
A. Load
B. Aluminium
C. Copper
D. Zinc
E. None of the above
Answer» C. Copper
Discussion
40.

A rotary converter in general construction and design, is more or less like___________?
A. a transformer
B. an induction motor
C. an alternator
D. any D.C. machine
Answer» E.
Discussion
41.

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
42.

In selenium rectifiers efficiencies ranging from _______ to _______ percent are attainable?
A. 25, 35
B. 40, 50
C. 60, 70
D. 75, 85
Answer» E.
Discussion
43.

In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of______________?
A. shunt motor
B. synchronous motor
C. induction regulator
D. synchronous generator
Answer» D. synchronous generator
Discussion
44.

Copper oxide rectifier is usually designed not to operate above___________?
A. 10°C
B. 20°C
C. 30°C
D. 45°C
Answer» E.
Discussion
45.

Which of the following statement is incorrect ?
A. Copper oxide rectifier is a linear device
B. Copper oxide rectifier is not a perfect rectifier
C. Copper oxide rectifier has a low efficiency
D. Copper oxide rectifier finds use in control circuits
E. Copper oxide rectifier is not stable during early life
Answer» B. Copper oxide rectifier is not a perfect rectifier
Discussion
46.

In phase-shift control method the control is carried out by varying the of grid voltage
A. magnitude
B. polarity
C. phase
D. any of the above
E. none of the above
Answer» D. any of the above
Discussion
47.

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
48.

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
49.

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
50.

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