Explore topic-wise MCQs in Electrical Engineering Questions.

This section includes 192 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.

When does the arc interruption in oil circuit breaker take place?
A. Contacts apart.
B. Voltages becomes zero
C. Current goes through zero
D. All of the above
Answer» D. All of the above
Discussion
2.

A short-circuit is identified by_____________?
A. no current flow
B. heavy current flow
C. voltage drop
D. voltage rise
Answer» C. voltage drop
Discussion
3.

The short circuit in any winding of the transformer is the result of______________?
A. mechanical vibration
B. insulation failure
C. loose connection
D. impulse voltage
Answer» E.
Discussion
4.

What does protective relay provide?
A. Provide additional safety to the circuit breaker in its operation.
B. Close the contacts when the actuating quantity attains a certain predetermined value.
C. Limit the arcing current during the circuit breaker operation.
D. Earth or ground any stray voltage.
Answer» C. Limit the arcing current during the circuit breaker operation.
Discussion
5.

Which of the following should have low value for the contacts and their material?
A. Thermal capacity.
B. Contact resistance.
C. Thermal conductivity.
D. None of above.
Answer» C. Thermal conductivity.
Discussion
6.

Which device sends the information to the circuit breaker to interrupt the circuit in case of fault?
A. Switch
B. Relay
C. Circuit breaker itself does this function.
D. Fuse
Answer» C. Circuit breaker itself does this function.
Discussion
7.

The heat produced at the contact point owing to flow of electric current is least affected by_____________________.
A. Temperature of the surrounding medium.
B. Contact resistance.
C. Magnitude of electric current flowing.
D. Duration of flow of current.
Answer» B. Contact resistance.
Discussion
8.

What is fusing factor?
A. The ratio of current rating of the fuse to the minimum fusing current
B. The ratio of minimum fusing current to the current rating of the fuse
C. The ratio of maximum fusing current to the current rating of the fuse
D. The ratio of minimum fusing current to the voltage rating of the fuse
Answer» C. The ratio of maximum fusing current to the current rating of the fuse
Discussion
9.

What is switchgear?
A. An apparatus used for switching, controlling and protecting the electrical circuits and equipments.
B. It detects the faults only.
C. It corrects the faults only.
D. All of the above.
Answer» E.
Discussion
10.

The arc voltage produced in A.C. circuit breaker is always_____________?
A. in phase with the arc current
B. lagging the arc current by 90″
C. leading the arc current by 90°
D. none of the above
Answer» B. lagging the arc current by 90″
Discussion
11.

What is the primary principle of a fuse?
A. Open the circuit.
B. Protect the appliance.
C. Protect the line.
D. Prevent excess current from flowing into the line.
Answer» E.
Discussion
12.

When does the circuit breaker operate in the line?
A. When power is to be supplied.
B. When the line is to be tested.
C. Whenever the fault occurs in the line.
D. Whenever the switch and the relay has to be operated.
Answer» D. Whenever the switch and the relay has to be operated.
Discussion
13.

Arcing voltage will be the least in case of
A. Carbon
B. Copper
C. Silver
D. Tungsten
Answer» D. Tungsten
Discussion
14.

Which material is used for the manufacture of bus bars?
A. Aluminium rods.
B. Copper rods.
C. Any conducting material.
D. Made of silver.
Answer» C. Any conducting material.
Discussion
15.

How is the bus bars rated?
A. Current only.
B. Voltage only.
C. Current, voltage and frequency.
D. Current, voltage, frequency and short circuit current.
Answer» E.
Discussion
16.

Which among these are the main characteristics of a fuse element?
A. Low melting point
B. High conductivity
C. Least deterioration due to oxidation
D. All of the above
Answer» E.
Discussion
17.

What is the arc voltage in a circuit breaker?
A. In phase with the arc current.
B. Lagging the arc current by 90°
C. Leading the arc current by 90°
D. Lagging the arcing current by 180°
Answer» B. Lagging the arc current by 90°
Discussion
18.

What happens in the arc extinction using high resistance method?
A. Arc resistance is decreased with time.
B. Arc resistance is increased with time.
C. No change it remains same.
D. Arc resistance is kept zero.
Answer» C. No change it remains same.
Discussion
19.

The resistance of an electric arc can be increased by
A. Increasing the concentration of ionised particles
B. Reducing the arc length.
C. Splitting the arc.
D. Increasing the arc cross section
Answer» D. Increasing the arc cross section
Discussion
20.

By using low resistance method for arc extension what is the value of arc resistance?
A. Arc resistance is zero.
B. Arc resistance is high
C. Arc resistance is low
D. Arc resistance is very high
Answer» D. Arc resistance is very high
Discussion
21.

Which among the following statement is true related to fuse?
A. Greater the current smaller is the time taken by the fuse to blow out.
B. Greater the current greater is the time taken by the fuse to blow out.
C. The current is directly proportion to the blow out time of fuse.
D. Is dependent on the temperature and atmospheric conditions.
Answer» B. Greater the current greater is the time taken by the fuse to blow out.
Discussion
22.

What should be the value of fusing factor?
A. Equal to zero
B. Equal to one
C. Less than one
D. More than one
Answer» D. More than one
Discussion
23.

If the strands of the fusing wire are twisted, what happens to the fusing current?
A. Increases
B. Reduces
C. No change/ remains same
D. Depends on the value of current, increases or decreases.
Answer» C. No change/ remains same
Discussion
24.

What is the maximum current upto which fuses can be used?
A. 25 A
B. 50 A
C. 75 A
D. 100 A
Answer» E.
Discussion
25.

A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9A. What will be the radius of the wire that will blow off at a current of 1A?
A. 0.2 mm
B. 0.18 mm
C. 0.28 mm
D. 0.3 mm
Answer» C. 0.28 mm
Discussion
26.

What is the typical value of the pre arcing time?
A. 0.1
B. 0.01
C. 0.001
D. 0.0001
Answer» D. 0.0001
Discussion
27.

Which material is used in the liquid type of fuse?
A. SF6
B. Distilled water
C. Carbon tetra chloride.
D. Mineral oil / transformer oil
Answer» D. Mineral oil / transformer oil
Discussion
28.

What is the advantage of HRC fuses over Rewirable fuses?
A. High speed operation
B. High rupturing capacity
C. No ageing effect.
D. All of the above.
Answer» E.
Discussion
29.

Which among these tests are performed to check the nation or international standards?
A. Type test.
B. Production tests.
C. Site checks.
D. All of the above.
Answer» B. Production tests.
Discussion
30.

Upto what voltage a cartridge type of fuse can be used?
A. 400 V
B. 11 kV
C. 20 kV
D. 33 kV
Answer» E.
Discussion
31.

What is the cut off current in the fuse?
A. Maximum value actually reached.
B. Rms value actually reached.
C. Average value actually reached.
D. None of the above
Answer» B. Rms value actually reached.
Discussion
32.

On what basis is the selection of fuse done?
A. Steady load.
B. Fluctuating load.
C. Both (a) and (b)
D. None of these.
Answer» D. None of these.
Discussion
33.

In a HRC fuse what is the time between the cut off and the final current zero called?
A. Pre - arcing time.
B. Arcing time.
C. Total operating time.
D. None of these.
Answer» C. Total operating time.
Discussion
34.

What is the main advantage of using a fuse?
A. Cheapest type of protection.
B. Inverse time current characteristics
C. Current limiting effect under short circuit conditions.
D. All of above.
Answer» E.
Discussion
35.

Upto what voltage can the liquid type HRC fuses be used?
A. 33 kV
B. 132 kV
C. 66 kV
D. 220 kV
Answer» C. 66 kV
Discussion
36.

When a fault occurs in a high voltage transmission line, what happens first?
A. Circuit breaker operates then the relay.
B. Relay operates and then the circuit breaker.
C. Relay operates, then successively the isolator and the circuit breaker.
D. Isolator operates, then successively the relay and the circuit breaker.
Answer» C. Relay operates, then successively the isolator and the circuit breaker.
Discussion
37.

Which type of tripping is generally preferred for the circuit breaker?
A. Manual
B. Automatically
C. Depending on the voltage level
D. None of the above
Answer» C. Depending on the voltage level
Discussion
38.

Which part of the circuit breaker is helpful in breaking the current?
A. Trip coil
B. Contacts
C. Medium
D. Handle
Answer» C. Medium
Discussion
39.

How is the initiation of electric arc at the instant of contact separation caused?
A. Thermionic emission of electrons.
B. Field emission of electrons.
C. Both (a) and (b)
D. None of these.
Answer» D. None of these.
Discussion
40.

The arc resistance depends on which among the following factors?
A. Cross section of the arc
B. Length of the arc
C. Degree of ionization
D. All of the above
Answer» E.
Discussion
41.

In a circuit breaker, ionisation is facilitated by_________________.
A. Increase in field strength
B. Increase in mean free length
C. High temperature of the surrounding medium
D. All of the above
Answer» E.
Discussion
42.

In a circuit breaker the contact space is ionised by what?
A. Field emission from the contact surface
B. Thermal emission from the contact surface
C. Thermal ionisation of gas
D. All of above
Answer» D. All of above
Discussion
43.

The interrupting time of a circuit breaker is the period between the instant of _________.
A. Initiation of short circuit and the arc extinction on an opening operation
B. Energizing the trip circuit and the arc extension on an opening operation
C. Initiation of short circuit and the parting of primary arc contacts
D. Energizing of the trip circuit and the parting of primary arc contacts
Answer» C. Initiation of short circuit and the parting of primary arc contacts
Discussion
44.

Which among these is the least expensive protection for over current in low voltage system?
A. Rewirable fuse.
B. Isolator
C. Circuit breaker.
D. Air breaker switch.
Answer» B. Isolator
Discussion
45.

For a current upto 10A which material is used as the fusing element?
A. Copper
B. Silver
C. Alloy of lead and tin
D. Zinc
Answer» D. Zinc
Discussion
46.

Large internal faults are protected by_______________?
A. merz price percentage differential protection
B. mho and ohm relays
C. horn gaps and temperature relays
D. earth fault and positive sequence relays
Answer» B. mho and ohm relays
Discussion
47.

Directional relays are based on flow of____________?
A. power
B. current
C. voltage wave
D. all of the above
Answer» B. current
Discussion
48.

The voltage appearing across the contacts after opening of the circuit breaker is called__________voltage
A. recovery
B. surge
C. operating
D. arc
E. none of the above
Answer» B. surge
Discussion
49.

Circuit breakers usually operate under______________?
A. transient state of short-circuit current
B. sub-transient state of short-circuit current
C. steady state of short-circuit current
D. after D.C. component has ceased
Answer» B. sub-transient state of short-circuit current
Discussion
50.

Protective relays are devices that detect abnormal conditions in electrical circuits by measuring_____________?
A. current during abnormal condition
B. voltage during abnormal condition
C. constantly the electrical quantities which differ during normal and abnormal conditions
D. none of the above
Answer» D. none of the above
Discussion