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.

101.

When using air blast circuit breaker, current chopping is a phenomenon observed when
A. A long overhead line is switched off.
B. A bank of capacitors is switched off.
C. A transformer on no load is switched off.
D. A heavy load is switched off.
Answer» D. A heavy load is switched off.
Discussion
102.

The air blast circuit breakers for 400 kV systems are designed to operate in how much time?
A. 0.1 s
B. 0.5 s
C. 50 ms
D. 100µs
Answer» D. 100µs
Discussion
103.

What is the type of air blast in cross blast type CB?
A. The blast of air is along the arc.
B. The blast of air cuts across the arc.
C. Both (a) and (b)
D. None of the above.
Answer» C. Both (a) and (b)
Discussion
104.

In axial blast type of CB, expansion of air takes place from ______________.
A. High pressure to low pressure.
B. Low pressure to high pressure.
C. Always in high pressure.
D. Always in low pressure.
Answer» B. Low pressure to high pressure.
Discussion
105.

To limit current chopping in vacuum circuit breakers, the contact material employed should have the properties of
A. Low conductivity and high vapour pressure.
B. Low conductivity and low vapour pressure.
C. High conductivity and high vapour pressure.
D. High conductivity and low vapour pressure.
Answer» B. Low conductivity and low vapour pressure.
Discussion
106.

What is the main purpose of oil in oil circuit breakers?
A. Provide insulation
B. Quenching arc.
C. Provide cooling of contacts.
D. None of the above
Answer» C. Provide cooling of contacts.
Discussion
107.

A thermal protection switch provides protection against what?
A. Overload
B. Temperature
C. Short circuit
D. Over voltage
Answer» B. Temperature
Discussion
108.

What is / are the main disadvantage / s of using oil as the quenching medium in the circuit breakers?
A. Need periodical replacement.
B. Risk of formation of explosive mixture with air.
C. Possibility of causing fire hazards.
D. All of the above.
Answer» E.
Discussion
109.

What is the advantage of using oil as the arc quenching medium?
A. Good cooling properties.
B. High dielectric strength.
C. Acts as an insulator.
D. All of these.
Answer» E.
Discussion
110.

What is the breaking capacity of the air blast circuit breaker?
A. 5000 MVA
B. 6000 MVA
C. 7000 MVA
D. 10000 MVA
Answer» D. 10000 MVA
Discussion
111.

A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current?
A. 1200 A
B. 3600 A
C. 35 kA
D. 104.8 kA
Answer» D. 104.8 kA
Discussion
112.

Which of the following circuit breakers is used for the railway electrification?
A. Air blast circuit breaker
B. SF6 circuit breaker
C. Bulk oil circuit breaker
D. Minimum oil circuit breaker
Answer» B. SF6 circuit breaker
Discussion
113.

With which of the following, a circuit breaker must be equipped for remote operation ?
A. Inverse time trip
B. Time-delay trip
C. Shunt trip
D. None of the above
E. All of the above
Answer» D. None of the above
Discussion
114.

The main function of a fuse is to_____________?
A. protect the line
B. open the circuit
C. protect the appliance
D. prevent excessive currents
E. none of the above
Answer» F.
Discussion
115.

Magnetic circuit breaker has ___________ trip action
A. delayed
B. instantaneous
C. both of the above
D. none of the above
Answer» C. both of the above
Discussion
116.

Fault diverters are basically____________?
A. fuses
B. relays
C. fast switches
D. circuit breakers
Answer» D. circuit breakers
Discussion
117.

Which among these circuit breakers produce the least arc energy?
A. Plain oil
B. Minimum oil
C. Air blast
D. Air break
Answer» D. Air break
Discussion
118.

The rating of the circuit breaker is usually determined on the basis of ____________ fault.
A. Symmetrical
B. Line to line
C. Single line to ground
D. Double line to ground
Answer» B. Line to line
Discussion
119.

Circuit breakers usually operate under
A. Steady short circuit current
B. Sub transient state of short circuit current
C. Transient state of short circuit current
D. None of these
Answer» C. Transient state of short circuit current
Discussion
120.

A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?
A. 35 kA
B. 49 kA
C. 70 kA
D. 89 kA
Answer» E.
Discussion
121.

What is the making capacity of the circuit breaker?
A. Less than the asymmetrical breaking capacity of the breaker
B. Greater than the asymmetrical breaking capacity of the breaker
C. Equal to the asymmetrical breaking capacity of the breaker
D. Equal to the symmetrical breaking capacity of the breaker
Answer» C. Equal to the asymmetrical breaking capacity of the breaker
Discussion
122.

What is the major cause of the failure of the circuit breaker?
A. Trip circuit open
B. Trip latch defective
C. Spring defective
D. All of these
Answer» E.
Discussion
123.

A fuse in a motor circuit provides protection against__________?
A. overload
B. short-circuit and overload
C. open circuit, short-circuit and overload
D. none of the above
Answer» C. open circuit, short-circuit and overload
Discussion
124.

The fuse wire, in D.C. circuits, is inserted in____________?
A. negative circuit only
B. positive circuit only
C. both (A) and (B)
D. either (A) or (B)
Answer» D. either (A) or (B)
Discussion
125.

What is the purpose of back up protection?
A. To increase the speed
B. To increase the reach
C. To leave no blind spot
D. To guard against failure of primary
Answer» E.
Discussion
126.

What is the actuating quantity for the relays?
A. Magnitude
B. Frequency
C. Phase angle
D. All of these
Answer» E.
Discussion
127.

Protective relays can be designed to respond to ___________.
A. Light intensity, impedance
B. Temperature, resistance, reactance
C. Voltage and current
D. All of these
Answer» E.
Discussion
128.

On what factor does the operating speed of the relay depend?
A. Rate of flux built up
B. Armature core air gap
C. Spring tension
D. All of these
Answer» E.
Discussion
129.

Plug setting of a electromagnetic relay can be altered by varying
A. Number of ampere turns
B. Air gap of magnetic path
C. Adjustable back stop
D. None of these
Answer» B. Air gap of magnetic path
Discussion
130.

The most efficient torque producing actuating structure for the induction type relays is
A. Shaded pole structure
B. Watt hour meter structure
C. Induction cup structure
D. Single induction loop structure
Answer» D. Single induction loop structure
Discussion
131.

The fuse blows off by___________?
A. burning
B. arcing
C. melting
D. none of the above
Answer» D. none of the above
Discussion
132.

Oil switches are employed for_____________?
A. low currents circuits
B. low voltages circuits
C. high voltages and large currents circuits
D. all circuits
Answer» D. all circuits
Discussion
133.

Protection by fuses is generally not used beyond__________?
A. 20 A
B. 50 A
C. 100 A
D. 200 A
Answer» D. 200 A
Discussion
134.

Air blast circuit breakers for 400 kV power system are designed to operate in_______________?
A. 100 microsecond
B. 50 millisecond
C. 0.5 sec
D. 0.1 sec
Answer» C. 0.5 sec
Discussion
135.

A switchgear is device used for_____________?
A. interrupting an electrical circuit
B. switching an electrical circuit 111.
C. switching and controlling an electrical circuit
D. switching, controlling and protecting the electrical circuit and equipment
Answer» E.
Discussion
136.

A fuse is never inserted in____________?
A. neutral wire
B. negative of D.C. circuit
C. positive of D.C. circuit
D. phase dine
Answer» B. negative of D.C. circuit
Discussion
137.

In a single bus-bar system there will be complete shut down when____________?
A. fault occurs on the bus itself
B. fault occurs on neutral line
C. two or more faults occur simultaneously
D. fault occurs with respect to earthing
Answer» B. fault occurs on neutral line
Discussion
138.

relays are used for phase faults on long line?
A. Impedance
B. Reactance
C. Either of the above
D. None of the above
Answer» B. Reactance
Discussion
139.

Overfluxing protection is recommended for_____________?
A. distribution transformer
B. generator transformer of the power plant
C. auto-transformer of the power plant
D. station transformer of the power plant
Answer» C. auto-transformer of the power plant
Discussion
140.

Induction cup relay is operated due to changes in________________?
A. current
B. voltage
C. impedance
D. all of the above
Answer» E.
Discussion
141.

If the fault occurs near the impedance relay, the VII ratio will be____________?
A. constant for all distances
B. lower than that of if fault occurs away from the relay
C. higher than that of if fault occurs away from the relay
D. none of the above
Answer» C. higher than that of if fault occurs away from the relay
Discussion
142.

relay is preferred for phase fault on short transmission line?
A. Induction type
B. Reactance
C. Impedance
D. None of the above
Answer» C. Impedance
Discussion
143.

For which of the following ratings of the transformer differential protection is recommended ?
A. above 30 kVA
B. equal to and above 5 MVA
C. equal to and above 25 MVA
D. none of the above
Answer» C. equal to and above 25 MVA
Discussion
144.

Series reactors should have________________?
A. low resistance
B. high resistance
C. low impedance
D. high impedance
Answer» B. high resistance
Discussion
145.

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
146.

The inverse definite mean time relays are used for over current and earth fault protection of transformer against_________________?
A. heavy loads
B. internal short-circuits
C. external short-circuits
D. all of the above
Answer» C. external short-circuits
Discussion
147.

Which of the following parameter can be neglected for a short line ?
A. Inductance
B. Capacitance
C. Resistance
D. Reactance
Answer» C. Resistance
Discussion
148.

Bus coupler is very essential in arrangement______________?
A. single bus
B. double bus, double breaker
C. main and transfer bus
D. all of the above
Answer» D. all of the above
Discussion
149.

The under voltage relay can be used for______________?
A. generators
B. busbars
C. transformers
D. motors
E. all of the above
Answer» F.
Discussion
150.

Insulation resistance of high voltage circuit breakers is more than________________?
A. 1 mega ohms
B. 10 mega ohms
C. 100 mega ohms
D. 500 mega ohms
Answer» D. 500 mega ohms
Discussion