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.

51.

SF6 gas______________?
A. is yellow in colour
B. is lighter than air
C. is nontoxic
D. has pungent small
E. none of the above
Answer» D. has pungent small
Discussion
52.

Air blast circuit breaker is used for_____________?
A. over currents
B. short duty
C. intermittant duty
D. repeated duty
Answer» E.
Discussion
53.

Circuit breakers are essentially____________?
A. current carrying contacts called electrodes
B. arc extinguishers
C. circuits to break the system
D. transformers to isolate the two systems
E. any of the above
Answer» B. arc extinguishers
Discussion
54.

Circuit breakers are essentially______________?
A. current carrying contacts called electrodes
B. arc extinguishers
C. circuits to break the system
D. transformers to isolate the two systems
E. any of the above
Answer» B. arc extinguishers
Discussion
55.

D.C. shunt relays are made of_____________?
A. few turns of thin wire
B. few turns of thick wire
C. many turns of thin wire
D. many turns of thick wire
Answer» D. many turns of thick wire
Discussion
56.

An efficient and a well designed protective relaying should have_____________?
A. good selectivity and reliability
B. economy and simplicity
C. high speed and selectivity
D. all of the above
Answer» E.
Discussion
57.

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties
Answer» E.
Discussion
58.

When a transmission line is energized, the wave that propagates on it is____________?
A. current wave only
B. voltage wave only
C. Both (A) and (B)
D. power factor wave only
Answer» D. power factor wave only
Discussion
59.

A differential relay measures the vector difference between_________________?
A. two currents
B. two voltages
C. two or more similar electrical quantities
D. none of the above
Answer» D. none of the above
Discussion
60.

The current zero interruption, in oil and air blast circuit breakers, is achieved by____________?
A. lengthening of the gap
B. cooling and blast effect
C. both (A) and (B)
D. deionizing the oil with forced air
E. none of the above
Answer» D. deionizing the oil with forced air
Discussion
61.

Shunt capacitance is neglected while considering______________?
A. short transmission line
B. medium transmission line
C. long transmission line
D. medium and long transmission lines
Answer» B. medium transmission line
Discussion
62.

The current zero interruption, in oil and air blast circuit breakers, is achieved by_______________?
A. lengthening of the gap
B. cooling and blast effect
C. both A. and B
D. deionizing the oil with forced air
E. none of the above
Answer» D. deionizing the oil with forced air
Discussion
63.

Burden of a protective relay is the power______________?
A. required to operate the circuit breaker
B. absorbed by the circuit of relay
C. developed by the relay circuit
D. none of the above
Answer» C. developed by the relay circuit
Discussion
64.

The relay operating speed depends upon_________________?
A. the spring tension
B. the rate of flux built up
C. armature core air gap
D. all of the above
Answer» E.
Discussion
65.

Relays can be designed to respond to changes in________________?
A. resistance, reactance or impedance
B. voltage and current
C. light intensity
D. temperature
E. all above
Answer» F.
Discussion
66.

Resistance grounding is used for voltage between_________________?
A. 33kVto66kV
B. HkVto33kV
C. 3.3kVandllkV
D. none of the above
Answer» D. none of the above
Discussion
67.

For the protection of power station buildings against direct strokes the requirements are___________?
A. interception
B. interception and conduction
C. interception, conduction and dissipation
D. interception, conduction, dissipation and reflection
E. none of the above
Answer» D. interception, conduction, dissipation and reflection
Discussion
68.

Interruption of large currents by relay requires______________?
A. arc suppressing blow out coils
B. wide separation of the opened contacts
C. high speed opening of contacts
D. all of the above
Answer» E.
Discussion
69.

Wave trap is used to trap waves of__________________?
A. power frequencies
B. higher frequencies entering generator or transformer units
C. either of the above
D. none of the above
Answer» C. either of the above
Discussion
70.

The ground wire should not be smaller than No _________ copper
A. 2
B. 4
C. 6
D. 10
Answer» E.
Discussion
71.

Overheating of relay contacts or contact born out is due to_______________?
A. slow making and breaking of load circuit contacts
B. foreign matter on the contact surface
C. too low contact pressure
D. all of the above
Answer» E.
Discussion
72.

Thermal overload relays are used to protect the motor against over current due to____________?
A. short-circuits
B. heavy loads
C. grounds
D. all of the above
Answer» C. grounds
Discussion
73.

A transmission line is protected by_____________?
A. inrush protection
B. distance protection
C. time graded and current graded over current protection
D. both (B) and (C)
E. none of the above
Answer» E. none of the above
Discussion
74.

Ionization in circuit breaker is facilitated by___________?
A. high temperature
B. increase of mean free path
C. increasing field strength
D. all of the above
Answer» E.
Discussion
75.

In a circuit breaker the basic problem is to________________?
A. maintain the arc
B. extinguish the arc
C. transmit large power
D. emit the ionizing electrons
Answer» D. emit the ionizing electrons
Discussion
76.

On what factor does the rate of rise of restriking voltage (RRRV) depend?
A. System voltage.
B. Circuit power factor only
C. Switching conditions
D. Both (b) and (c).
Answer» E.
Discussion
77.

Overload relays are of_______________type
A. induction
B. solid state
C. thermal
D. electromagnetic
E. all above
Answer» F.
Discussion
78.

A thermal protection switch can protect against_____________?
A. short-circuit
B. temperature
C. overload
D. over voltage
Answer» D. over voltage
Discussion
79.

Which of the following medium is employed for extinction of arc in air circuit breaker?
A. Water
B. Oil
C. Air
D. SF6
Answer» D. SF6
Discussion
80.

On which of the following routine tests are conducted ?
A. Oil circuit breakers
B. Air blast circuit breakers
C. Minimum oil circuit breakers
D. All of the above
Answer» E.
Discussion
81.

Why is it difficult to interrupt a capacitive circuit?
A. The current has a leading power factor.
B. The restriking voltage can be high.
C. Current magnitude is very small.
D. Stored energy in the capacitor is very high.
Answer» C. Current magnitude is very small.
Discussion
82.

The stability of arc in vacuum depends on _________.
A. The contact material only.
B. The circuit parameters only.
C. The contact materials and its vapour pressure.
D. Both (b) and (c)
E. None of these
Answer» E. None of these
Discussion
83.

The arcing contacts in a circuit breaker are made of______________?
A. copper tungsten alloy
B. porcelain
C. electrolytic copper
D. aluminium alloy
Answer» B. porcelain
Discussion
84.

What is restriking voltage?
A. The transient voltage that appears across the circuit breaker contacts at the instant of arc extinction.
B. The transient voltage that appears across the circuit breaker contacts at the end of arc extinction.
C. Both (a) and (b)
D. None of the above
Answer» B. The transient voltage that appears across the circuit breaker contacts at the end of arc extinction.
Discussion
85.

For a high speed circuit breaker what will the total clearing time?
A. Few minutes.
B. Few seconds.
C. 1 to 2 cycles.
D. 5 to 20 cycles.
Answer» D. 5 to 20 cycles.
Discussion
86.

In a circuit breaker, the active recovery voltage depends upon which among these?
A. Circuit conditions.
B. Power factor.
C. Both (a) and (b)
D. None of the above
Answer» D. None of the above
Discussion
87.

Rate of rise of restriking voltage depend on_____________?
A. Type of circuit breaker.
B. Capacitance of the system.
C. Inductance of the system
D. Both (b) and (c)
E. None of these
Answer» E. None of these
Discussion
88.

What is the interrupting medium in the contactor?
A. Air at atmospheric pressure.
B. SF6 gas
C. Oil
D. All of the above.
Answer» E.
Discussion
89.

Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________
A. Restriking voltage
B. Final arc extinction
C. Rise of voltage
D. All of the above
Answer» C. Rise of voltage
Discussion
90.

How is the restriking voltage measured?
A. RMS value
B. Peak value
C. Instantaneous value
D. Average value
Answer» C. Instantaneous value
Discussion
91.

The torque produced in induction type relay (shaded pole structure) is_____________?
A. inversely proportional to the current
B. inversely proportional to the square of the current
C. proportional to the current
D. proportional to square of the current
Answer» C. proportional to the current
Discussion
92.

To limit short-circuit current in a power system are used______________?
A. earth wires
B. isolators
C. H.R.C. fuses
D. reactors
Answer» E.
Discussion
93.

The inductive interference between power and communication line can be minimized by__________?
A. transposition of the power line
B. transposition of the communication line
C. both (A) and (B)
D. increasing the distance between the conductors
Answer» D. increasing the distance between the conductors
Discussion
94.

Admittance relay is __________ relay?
A. impedance
B. directional
C. non-directional
D. none of the above
Answer» C. non-directional
Discussion
95.

The making and breaking currents of a 3 phase ac circuit breakers in power systems are respectively in ________form.
A. rms value, rms value
B. instantaneous value, rms value
C. rms value, instantaneous value
D. instantaneous value, instantaneous value
Answer» E.
Discussion
96.

In a short circuit test on a circuit breaker, the following readings were obtained on single frequency transients a. Time to reach the peak re striking voltage - 50μ sec b. The peak re striking voltage, 100 kV what will be the frequency of oscillations?
A. 100 Hz
B. 1,000 Hz
C. 10,000 Hz
D. 10 Hz
Answer» D. 10 Hz
Discussion
97.

Refer to the following facts to answer the question, A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 μ F. What is the peak re striking voltage?
A. 18.36 kV
B. 17.96 kV
C. 15.96 kV
D. 12.65 kV
Answer» C. 15.96 kV
Discussion
98.

Refer to the following facts to answer the question A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 μ F. What is the frequency of oscillations?
A. 10000 Hz
B. 12500 Hz
C. 12628 Hz
D. 13265 Hz
Answer» D. 13265 Hz
Discussion
99.

A 50 Hz 3 phase synchronous generator has inductance per phase of 15mH. The capacitance of generator and the circuit breaker is 0.002μ F. What is the natural frequency of oscillation?
A. 29 kHz
B. 2.9 kHz
C. 290 kHz
D. 29 MHz
Answer» B. 2.9 kHz
Discussion
100.

Why is the resistance switching used in a air blast circuit breaker?
A. Reduce the magnitude of fault current.
B. Control the CB operating time.
C. Damp out the fast transient.
D. Change the fault current power factor.
Answer» D. Change the fault current power factor.
Discussion