McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 101. |
What is the actuating quantity for the relays? |
| A. | Magnitude |
| B. | Frequency |
| C. | Phase angle |
| D. | All of these |
| Answer» D. All of these | |
| 102. |
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» D. All of the above | |
| 103. |
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» B. Greater than the asymmetrical breaking capacity of the breaker | |
| 104. |
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» C. Thermal ionisation of gas. | |
| 105. |
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» C. 35 kA | |
| 106. |
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» C. Less than one | |
| 107. |
What is the relation between the fusing current and the diameter of the wire? |
| A. | I = k d3 |
| B. | I = k d3/2 |
| C. | I = k d2 |
| D. | I = k d2/3 |
| Answer» B. I = k d3/2 | |
| 108. |
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» D. instantaneous value, instantaneous value | |
| 109. |
Why is an isolator installed? |
| A. | To isolate one portion of the circuit from another |
| B. | As an substitute for the circuit breaker |
| C. | It used on either sides of the circuit breaker |
| D. | Both (a) and (c) |
| Answer» A. To isolate one portion of the circuit from another | |
| 110. |
Assertion (A): In comparison to making capacity of a circuit breaker its breaking capacity is normally higher. Reason (R): The breaking capacity of a CB is expressed as √3 * VI * 10-6 MVA |
| A. | Both A and R are true and R is the correct explanation of A |
| B. | Both A and R are true and R is not the explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true. |
| Answer» D. A is false but R is true. | |
| 111. |
What is the cut off current in the fuse? |
| A. | Maximum value actually reache(D) |
| B. | Rms value actually reache(D) |
| C. | Average value actually reach |
| Answer» A. Maximum value actually reache(D) | |
| 112. |
Which circuit breaker is preferred to be installed in extra high voltage AC system? |
| A. | Bulk oil type circuit breaker |
| B. | Air blast circuit breaker |
| C. | SF6 circuit breaker |
| D. | Vacuum circuit breaker |
| Answer» C. SF6 circuit breaker | |
| 113. |
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» D. 89 kA | |
| 114. |
A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9(A) 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» B. 0.18 mm | |
| 115. |
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» A. Type test. | |
| 116. |
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» C. 12628 Hz | |
| 117. |
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» D. All of the above. | |
| 118. |
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» D. All of the above. | |
| 119. |
Which of the following circuit breakers has the lowest operating voltage? |
| A. | SF6 circuit breaker |
| B. | Air break |
| C. | Air blast |
| D. | Minimum oil circuit breaker |
| Answer» B. Air break | |
| 120. |
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» C. Induction cup structure | |
| 121. |
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» A. Number of ampere turns | |
| 122. |
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» B. Copper rods. | |
| 123. |
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» B. Relay | |
| 124. |
When does the circuit breaker operate in the line? |
| A. | When power is to be supplie(D) |
| B. | When the line is to be teste(D) |
| C. | Whenever the fault occurs in the line. |
| D. | Whenever the switch and the relay has to be operate(D) |
| Answer» C. Whenever the fault occurs in the line. | |
| 125. |
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» D. Prevent excess current from flowing into the line. | |
| 126. |
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» D. All of these | |
| 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» D. All of these | |
| 128. |
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» D. To guard against failure of primary | |
| 129. |
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» D. All of these | |
| 130. |
Why are the isolators used? |
| A. | Break abnormal current |
| B. | Making under fault conditions |
| C. | Breaking the circuit under no load condition |
| D. | None of the above |
| Answer» C. Breaking the circuit under no load condition | |
| 131. |
The isolators used in the transmission lines are capable of breaking |
| A. | Fault current |
| B. | No current |
| C. | Charging current |
| D. | Load current |
| Answer» C. Charging current | |
| 132. |
For which among the following the current ratings are not required? |
| A. | Circuit breakers |
| B. | Relays |
| C. | Isolators |
| D. | Load break switch |
| Answer» C. Isolators | |
| 133. |
What is the making to breaking current ratio for an extra high voltage circuit breaker? |
| A. | More than 1 |
| B. | Equal to 1 |
| C. | Less than 1 |
| D. | A negative value |
| Answer» A. More than 1 | |
| 134. |
The breaking capacity of a three phase circuit breaker is given by |
| A. | Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| B. | √3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| C. | 1.1* Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| D. | √2 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA |
| Answer» B. √3 * Service line voltage * rated symmetrical current in amperes * 10-6 MVA | |
| 135. |
Which of the following circuit breaker is highly reliable and has a least maintenance? |
| A. | Oil circuit breakers |
| B. | Air blast |
| C. | Vacuum circuit breakers |
| D. | SF6 circuit breakers |
| Answer» D. SF6 circuit breakers | |
| 136. |
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» A. Symmetrical | |
| 137. |
Which among these circuit breakers produce the least arc energy? |
| A. | Plain oil |
| B. | Minimum oil |
| C. | Air blast |
| D. | Air break |
| Answer» C. Air blast | |
| 138. |
A thermal protection switch provides protection against what? |
| A. | Overload |
| B. | Temperature |
| C. | Short circuit |
| D. | Over voltage |
| Answer» A. Overload | |
| 139. |
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» B. Close the contacts when the actuating quantity attains a certain predetermined value. | |
| 140. |
What is the main purpose of oil in oil circuit breakers? |
| A. | Provide insulation |
| B. | Quenching ar(C) |
| C. | Provide cooling of contacts. |
| D. | None of the above |
| Answer» B. Quenching ar(C) | |
| 141. |
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» D. All of these. | |
| 142. |
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» C. Current goes through zero | |
| 143. |
For rural electrification in India, which circuit breaker is generally used? |
| A. | Oil |
| B. | SF6 |
| C. | Vacuum |
| D. | Air blast |
| Answer» C. Vacuum | |
| 144. |
Keeping in view the cost and the overall effectiveness, which of the following circuit breaker is best suited for capacitor bank switching? |
| A. | Vacuum circuit breaker |
| B. | Air blast CB |
| C. | SF6 |
| D. | Oil CB |
| Answer» A. Vacuum circuit breaker | |
| 145. |
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» A. Low conductivity and high vapour pressure. | |
| 146. |
SF6 gas is imported in _____________. |
| A. | Air cylinders |
| B. | Gas cylinders |
| C. | Liquid form in cylinders |
| D. | Solid form. |
| Answer» C. Liquid form in cylinders | |
| 147. |
During arc extinction SF6 gas gets converted to which among these? |
| A. | Gets decomposed to SF4 and SF2 |
| B. | Gets decomposed to S and F |
| C. | Gets reduced to SF6 |
| D. | Gets oxidized |
| Answer» A. Gets decomposed to SF4 and SF2 | |
| 148. |
What is the most important property which makes the SF6 very efficient medium for circuit breaking? |
| A. | Is non toxic and non inflammable. |
| B. | Has a high dielectric constant. |
| C. | Has a high breakdown strength |
| D. | Is highly electronegative gas |
| Answer» D. Is highly electronegative gas | |
| 149. |
What is the normal pressure at which the SF6 gas is maintained in the closed position of the breaker? |
| A. | 2 kg / cm2 |
| B. | 2.5 kg /cm2 |
| C. | 2.8 kg / cm2 |
| D. | 3 kg / cm2 |
| Answer» C. 2.8 kg / cm2 | |
| 150. |
What is the major drawback of using SF6 circuit breakers? |
| A. | Sealing problems of the gas. |
| B. | Ingress of moisture in the gas system – dangerous. |
| C. | Deterioration of SF6 gas with time. |
| D. | Both (a) and (b) |
| Answer» D. Both (a) and (b) | |
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