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81. Lockout-tagout (LOTO) procedures during electrical maintenance are primarily intended to:
- A. Increase the speed of maintenance work by removing all safety checks
- B. Replace the need for personal protective equipment entirely
- C. Allow multiple people to energize the same circuit simultaneously without coordination
- D. Prevent equipment from being unexpectedly re-energized while maintenance personnel are working on it
Answer: Prevent equipment from being unexpectedly re-energized while maintenance personnel are working on it
Explanation: Prevent equipment from being unexpectedly re-energized while maintenance personnel are working on it — verified fact for Railway Electrical Engineering Group B LDCE.
82. Before working on any electrical equipment/circuit, the standard safety practice of 'permit to work' after isolation is primarily meant to:
- A. Speed up the work by skipping isolation checks
- B. Allow work on live circuits without any precaution
- C. Formally confirm the circuit has been de-energized, isolated, and earthed before staff begin work, preventing accidental re-energization
- D. Replace the need for any earthing during maintenance
Answer: Formally confirm the circuit has been de-energized, isolated, and earthed before staff begin work, preventing accidental re-energization
Explanation: Formally confirm the circuit has been de-energized, isolated, and earthed before staff begin work, preventing accidental re-energization — verified fact for Railway Electrical Engineering Group B LDCE.
83. Double insulation in certain electrical hand tools is a safety feature that mainly:
- A. Eliminates the need for any earthing on all equipment universally
- B. Doubles the voltage the tool can handle safely
- C. Provides two independent layers of insulation so a single insulation failure does not expose live parts
- D. Doubles the tool's power output
Answer: Provides two independent layers of insulation so a single insulation failure does not expose live parts
Explanation: Provides two independent layers of insulation so a single insulation failure does not expose live parts — verified fact for Railway Electrical Engineering Group B LDCE.
84. A residual current device (RCD)/earth leakage circuit breaker is designed to trip mainly when it detects:
- A. A drop in ambient temperature
- B. A change in the colour of the wiring insulation
- C. An increase in the number of trains running
- D. An imbalance between line and neutral current, indicating current leaking to earth (possibly through a person)
Answer: An imbalance between line and neutral current, indicating current leaking to earth (possibly through a person)
Explanation: An imbalance between line and neutral current, indicating current leaking to earth (possibly through a person) — verified fact for Railway Electrical Engineering Group B LDCE.
85. Basic electrical safety practice requires that exposed metal parts of electrical equipment (not meant to carry current) be earthed mainly to:
- A. Increase the power output of the equipment
- B. Provide a safe path for fault current and prevent dangerous voltage on the equipment casing if insulation fails
- C. Reduce the equipment's electricity bill directly
- D. Improve the appearance of the equipment
Answer: Provide a safe path for fault current and prevent dangerous voltage on the equipment casing if insulation fails
Explanation: Provide a safe path for fault current and prevent dangerous voltage on the equipment casing if insulation fails — verified fact for Railway Electrical Engineering Group B LDCE.
86. A star-delta starter is commonly used for large induction motors mainly to:
- A. Permanently reduce the motor's running speed
- B. Eliminate the need for any motor winding
- C. Reduce the high starting current drawn compared to direct-on-line starting
- D. Convert the motor from AC to DC operation
Answer: Reduce the high starting current drawn compared to direct-on-line starting
Explanation: Reduce the high starting current drawn compared to direct-on-line starting — verified fact for Railway Electrical Engineering Group B LDCE.
87. An induction motor is generally described as 'self-starting' (in the three-phase case) because:
- A. The rotating magnetic field produced by the three-phase stator winding induces rotor current and torque without external starting aids
- B. It can only run when connected to a battery
- C. It always needs a separate DC starting motor to begin turning
- D. It requires no electrical supply at all to begin rotating
Answer: The rotating magnetic field produced by the three-phase stator winding induces rotor current and torque without external starting aids
Explanation: The rotating magnetic field produced by the three-phase stator winding induces rotor current and torque without external starting aids — verified fact for Railway Electrical Engineering Group B LDCE.
88. The synchronous speed of a three-phase induction motor depends primarily on:
- A. The ambient humidity only
- B. The colour of the motor casing
- C. The length of connecting cables only
- D. Supply frequency and the number of poles in the motor
Answer: Supply frequency and the number of poles in the motor
Explanation: Supply frequency and the number of poles in the motor — verified fact for Railway Electrical Engineering Group B LDCE.
89. A three-phase induction motor's rotor generally rotates at a speed slightly less than the synchronous speed; this difference is called:
- A. Reactance
- B. Impedance
- C. Torque
- D. Slip
Answer: Slip
Explanation: Slip — verified fact for Railway Electrical Engineering Group B LDCE.
90. The commutator in a DC motor primarily functions to:
- A. Cool the motor windings
- B. Step up the supply voltage
- C. Periodically reverse the current direction in the armature windings to maintain continuous rotation in one direction
- D. Generate the magnetic field independently of any winding
Answer: Periodically reverse the current direction in the armature windings to maintain continuous rotation in one direction
Explanation: Periodically reverse the current direction in the armature windings to maintain continuous rotation in one direction — verified fact for Railway Electrical Engineering Group B LDCE.
91. Fleming's right-hand rule is commonly used to determine the direction of:
- A. Induced EMF/current in a conductor moving through a magnetic field (as in a generator)
- B. The resistance of a circuit
- C. The polarity of a battery only
- D. Force on a current-carrying conductor in a motor
Answer: Induced EMF/current in a conductor moving through a magnetic field (as in a generator)
Explanation: Induced EMF/current in a conductor moving through a magnetic field (as in a generator) — verified fact for Railway Electrical Engineering Group B LDCE.
92. Fleming's left-hand rule is commonly used to determine the direction of:
- A. Frequency of an AC supply
- B. Force on a current-carrying conductor in a magnetic field (as in a motor)
- C. Resistance value of a conductor
- D. Induced EMF in a generator only
Answer: Force on a current-carrying conductor in a magnetic field (as in a motor)
Explanation: Force on a current-carrying conductor in a magnetic field (as in a motor) — verified fact for Railway Electrical Engineering Group B LDCE.
93. A DC motor's basic working principle relies on the force experienced by a current-carrying conductor placed in a magnetic field, described by:
- A. The law of conservation of mass
- B. The motor principle (F = BIL), related to Fleming's left-hand rule
- C. Ohm's Law exclusively
- D. Kirchhoff's Voltage Law exclusively
Answer: The motor principle (F = BIL), related to Fleming's left-hand rule
Explanation: The motor principle (F = BIL), related to Fleming's left-hand rule — verified fact for Railway Electrical Engineering Group B LDCE.
94. Iron (core) losses in a transformer, comprising hysteresis and eddy current losses, occur mainly in the:
- A. Transformer's external tank paint
- B. Magnetic core of the transformer
- C. Cooling fan blades
- D. Copper windings exclusively
Answer: Magnetic core of the transformer
Explanation: Magnetic core of the transformer — verified fact for Railway Electrical Engineering Group B LDCE.
95. Copper losses in a transformer are primarily caused by:
- A. Resistance (I²R heating) of the primary and secondary windings
- B. Hysteresis in the core material exclusively
- C. Eddy currents in the core exclusively
- D. Air friction around the transformer tank
Answer: Resistance (I²R heating) of the primary and secondary windings
Explanation: Resistance (I²R heating) of the primary and secondary windings — verified fact for Railway Electrical Engineering Group B LDCE.
96. The core of a power transformer is typically made of laminated silicon steel mainly to:
- A. Eliminate the need for any winding
- B. Increase the transformer's weight for stability
- C. Reduce eddy current losses while maintaining good magnetic properties
- D. Increase electrical conductivity of the core to carry load current
Answer: Reduce eddy current losses while maintaining good magnetic properties
Explanation: Reduce eddy current losses while maintaining good magnetic properties — verified fact for Railway Electrical Engineering Group B LDCE.
97. A transformer can only step voltage up or down for which type of supply?
- A. Alternating current (AC) supply
- B. Any supply, whether AC or steady DC, identically
- C. Pure direct current (DC) supply only
- D. Only mechanical, non-electrical inputs
Answer: Alternating current (AC) supply
Explanation: Alternating current (AC) supply — verified fact for Railway Electrical Engineering Group B LDCE.
98. The basic working principle of a transformer relies on:
- A. Chemical reaction between two electrodes
- B. Direct electrical connection between primary and secondary windings
- C. Mechanical friction between two coils
- D. Mutual electromagnetic induction between two windings linked by a common magnetic flux
Answer: Mutual electromagnetic induction between two windings linked by a common magnetic flux
Explanation: Mutual electromagnetic induction between two windings linked by a common magnetic flux — verified fact for Railway Electrical Engineering Group B LDCE.
99. In a purely capacitive AC circuit, the current:
- A. Lags the voltage by 90 degrees
- B. Cannot flow at all in a capacitor
- C. Leads the voltage by 90 degrees
- D. Is exactly in phase with the voltage
Answer: Leads the voltage by 90 degrees
Explanation: Leads the voltage by 90 degrees — verified fact for Railway Electrical Engineering Group B LDCE.
100. In a purely inductive AC circuit, the current:
- A. Leads the voltage by 90 degrees
- B. Is exactly in phase with the voltage
- C. Lags the voltage by 90 degrees
- D. Is always zero regardless of voltage
Answer: Lags the voltage by 90 degrees
Explanation: Lags the voltage by 90 degrees — verified fact for Railway Electrical Engineering Group B LDCE.
101. In a purely resistive AC circuit, the voltage and current waveforms are:
- A. In phase with each other
- B. 90 degrees out of phase
- C. 180 degrees out of phase always
- D. Completely unrelated to each other
Answer: In phase with each other
Explanation: In phase with each other — verified fact for Railway Electrical Engineering Group B LDCE.
102. Ohm's Law states that, for a conductor at constant temperature, the current through it is:
- A. Completely independent of the applied voltage
- B. Inversely proportional to the voltage across it
- C. Directly proportional to the voltage across it, for constant resistance
- D. Proportional to the square of the resistance only
Answer: Directly proportional to the voltage across it, for constant resistance
Explanation: Directly proportional to the voltage across it, for constant resistance — verified fact for Railway Electrical Engineering Group B LDCE.
103. In a balanced three-phase circuit with line voltage 400V, line current 10A, and power factor 0.8, the three-phase real power (using P = √3 × VL × IL × cosφ) is approximately:
- A. Approximately 4 kW
- B. Approximately 3.2 kW
- C. Approximately 8 kW
- D. Approximately 5.54 kW
Answer: Approximately 5.54 kW
Explanation: Approximately 5.54 kW — verified fact for Railway Electrical Engineering Group B LDCE.
104. In a single-phase AC circuit with V = 230V, I = 10A, and a power factor of 0.9, the real (active) power consumed is approximately:
- A. 2300 W
- B. 4140 W
- C. 1035 W
- D. 2070 W
Answer: 2070 W
Explanation: 2070 W — verified fact for Railway Electrical Engineering Group B LDCE.
105. If a 1000W (1kW) electrical heater is run continuously for 5 hours, the energy consumed, expressed in units (kWh), is:
- A. 50 kWh
- B. 0.5 kWh
- C. 500 kWh
- D. 5 kWh (5 units)
Answer: 5 kWh (5 units)
Explanation: 5 kWh (5 units) — verified fact for Railway Electrical Engineering Group B LDCE.
106. Two equal resistors of 10 ohms each are connected in parallel. The equivalent resistance of this parallel combination is:
- A. 2.5 ohms
- B. 10 ohms
- C. 5 ohms
- D. 20 ohms
Answer: 5 ohms
Explanation: 5 ohms — verified fact for Railway Electrical Engineering Group B LDCE.
107. Two resistors of 10 ohms and 20 ohms are connected in series across a supply. The total (equivalent) resistance of the combination is:
- A. 30 ohms
- B. 6.67 ohms
- C. 10 ohms
- D. 200 ohms
Answer: 30 ohms
Explanation: 30 ohms — verified fact for Railway Electrical Engineering Group B LDCE.
108. Using the formula P = V²/R, a 200V supply connected across a 50-ohm resistor dissipates a power of:
- A. 800 W
- B. 400 W
- C. 4 W
- D. 80 W
Answer: 800 W
Explanation: 800 W — verified fact for Railway Electrical Engineering Group B LDCE.
109. A resistive heating element draws 5A of current through a resistance of 10 ohms. Using P = I²R, the power dissipated is:
- A. 2500 W
- B. 50 W
- C. 500 W
- D. 250 W
Answer: 250 W
Explanation: 250 W — verified fact for Railway Electrical Engineering Group B LDCE.
110. A circuit carries a current of 2A at a voltage of 230V. The electrical power consumed is:
- A. 460 W
- B. 115 W
- C. 23 W
- D. 920 W
Answer: 460 W
Explanation: 460 W — verified fact for Railway Electrical Engineering Group B LDCE.
111. According to Ohm's Law, if a circuit has a voltage of 230V and a resistance of 100 ohms, the current flowing through it is:
- A. 230 A
- B. 2.3 A
- C. 23 A
- D. 0.23 A
Answer: 2.3 A
Explanation: 2.3 A — verified fact for Railway Electrical Engineering Group B LDCE.
112. An electric locomotive's traction motor ventilation/cooling and power converter cooling are both examples of subsystems designed mainly to:
- A. Generate the locomotive's main traction supply
- B. Increase the OHE's mechanical tension
- C. Control the signalling system at the next station
- D. Prevent overheating of high-power electrical equipment during continuous operation
Answer: Prevent overheating of high-power electrical equipment during continuous operation
Explanation: Prevent overheating of high-power electrical equipment during continuous operation — verified fact for Railway Electrical Engineering Group B LDCE.
113. Onboard earthing/bonding of the locomotive body to the running rails (via wheels) is important mainly because it helps:
- A. Increase the locomotive's top speed
- B. Eliminate the need for a pantograph
- C. Change the phase of the traction supply
- D. Complete the return current path safely and reduce the risk of dangerous voltages on the locomotive body
Answer: Complete the return current path safely and reduce the risk of dangerous voltages on the locomotive body
Explanation: Complete the return current path safely and reduce the risk of dangerous voltages on the locomotive body — verified fact for Railway Electrical Engineering Group B LDCE.
114. A locomotive's main circuit breaker (MCB), located on the roof or inside the locomotive, is used to:
- A. Connect or disconnect the locomotive's electrical circuits from the pantograph/OHE supply
- B. Change the track the train runs on
- C. Control the train's braking system mechanically only
- D. Adjust the signalling aspect
Answer: Connect or disconnect the locomotive's electrical circuits from the pantograph/OHE supply
Explanation: Connect or disconnect the locomotive's electrical circuits from the pantograph/OHE supply — verified fact for Railway Electrical Engineering Group B LDCE.
115. Speedometers and event recorders on modern electric locomotives are examples of onboard systems that primarily support:
- A. Ticket checking on board
- B. Safe operation monitoring and post-incident analysis of the locomotive's running parameters
- C. Direct control of OHE tensioning devices
- D. Generation of the traction supply voltage
Answer: Safe operation monitoring and post-incident analysis of the locomotive's running parameters
Explanation: Safe operation monitoring and post-incident analysis of the locomotive's running parameters — verified fact for Railway Electrical Engineering Group B LDCE.
116. A key advantage of multiple-unit (MU) operation of locomotives on heavy freight trains is:
- A. Automatic doubling of the train's maximum speed
- B. Combined higher tractive effort for hauling heavier loads, controlled by a single loco pilot
- C. Removal of the requirement for any OHE
- D. Complete elimination of the need for any traction power
Answer: Combined higher tractive effort for hauling heavier loads, controlled by a single loco pilot
Explanation: Combined higher tractive effort for hauling heavier loads, controlled by a single loco pilot — verified fact for Railway Electrical Engineering Group B LDCE.
117. The term 'multiple unit operation' when applied to locomotives (as opposed to EMUs) refers to:
- A. Coupling two or more locomotives together, controlled from a single leading cab
- B. Operating only diesel locomotives, never electric
- C. Splitting one locomotive into multiple independent units physically
- D. Running a single locomotive with no coupling at all
Answer: Coupling two or more locomotives together, controlled from a single leading cab
Explanation: Coupling two or more locomotives together, controlled from a single leading cab — verified fact for Railway Electrical Engineering Group B LDCE.
118. A dual-cab electric locomotive design (with driving controls at both ends) mainly allows:
- A. Operation in either direction without needing to turn the locomotive around
- B. Elimination of the need for a pantograph on one end
- C. Automatic regenerative braking with no other requirement
- D. Doubling of the traction motor power output
Answer: Operation in either direction without needing to turn the locomotive around
Explanation: Operation in either direction without needing to turn the locomotive around — verified fact for Railway Electrical Engineering Group B LDCE.
119. A pantograph being lowered automatically (or by the loco pilot) when passing certain OHE-free zones (like some yards) is a safety measure mainly to:
- A. Prevent mechanical damage to the pantograph or nearby structures where no OHE is present or clearance is restricted
- B. Increase the train's speed in that zone
- C. Charge the locomotive's battery faster
- D. Change the signalling aspect automatically
Answer: Prevent mechanical damage to the pantograph or nearby structures where no OHE is present or clearance is restricted
Explanation: Prevent mechanical damage to the pantograph or nearby structures where no OHE is present or clearance is restricted — verified fact for Railway Electrical Engineering Group B LDCE.
120. Air-conditioning equipment on modern passenger coaches draws its electrical supply typically from:
- A. The signalling telecom network
- B. The wheel-slip control system
- C. A separate independent traction substation dedicated only to air-conditioning
- D. The head-on generation supply from the locomotive or an onboard/end-on power source
Answer: The head-on generation supply from the locomotive or an onboard/end-on power source
Explanation: The head-on generation supply from the locomotive or an onboard/end-on power source — verified fact for Railway Electrical Engineering Group B LDCE.
121. A locomotive's control circuit typically operates at a much lower voltage than the traction circuit mainly for reasons of:
- A. Because lower voltage always produces more power
- B. Safety and practicality for switches, relays, and electronic control equipment handled by staff
- C. Because the OHE cannot supply high voltage to any locomotive circuit
- D. Because low voltage eliminates the need for insulation
Answer: Safety and practicality for switches, relays, and electronic control equipment handled by staff
Explanation: Safety and practicality for switches, relays, and electronic control equipment handled by staff — verified fact for Railway Electrical Engineering Group B LDCE.
122. A locomotive's battery (typically low-voltage DC) is important mainly for supplying power to:
- A. Signal interlocking logic at the station
- B. Control circuits, instrumentation, and essential systems when the main supply is unavailable (e.g. pantograph down)
- C. The entire OHE feeding system
- D. The full traction motor load during normal running
Answer: Control circuits, instrumentation, and essential systems when the main supply is unavailable (e.g. pantograph down)
Explanation: Control circuits, instrumentation, and essential systems when the main supply is unavailable (e.g. pantograph down) — verified fact for Railway Electrical Engineering Group B LDCE.
123. Wheel-slip control systems on electric locomotives are important mainly because they help:
- A. Increase the traction voltage supplied by the OHE
- B. Eliminate the need for a pantograph
- C. Maintain optimal adhesion between wheel and rail, preventing wasteful or damaging wheel spin/slip
- D. Directly control the signalling aspects
Answer: Maintain optimal adhesion between wheel and rail, preventing wasteful or damaging wheel spin/slip
Explanation: Maintain optimal adhesion between wheel and rail, preventing wasteful or damaging wheel spin/slip — verified fact for Railway Electrical Engineering Group B LDCE.
124. A locomotive's traction motor blower (cooling fan) is essential mainly because it:
- A. Increases the locomotive's top speed directly
- B. Powers the pantograph's raising mechanism
- C. Removes heat generated by the traction motor during operation, preventing overheating
- D. Generates the traction motor's supply voltage
Answer: Removes heat generated by the traction motor during operation, preventing overheating
Explanation: Removes heat generated by the traction motor during operation, preventing overheating — verified fact for Railway Electrical Engineering Group B LDCE.
125. IGBTs (Insulated Gate Bipolar Transistors) are commonly used in modern locomotive traction converters mainly because they act as:
- A. Mechanical brakes for the wheels
- B. Insulators for the OHE contact wire
- C. Generators of the primary 25kV supply
- D. High-power semiconductor switches enabling efficient control of voltage and frequency
Answer: High-power semiconductor switches enabling efficient control of voltage and frequency
Explanation: High-power semiconductor switches enabling efficient control of voltage and frequency — verified fact for Railway Electrical Engineering Group B LDCE.
126. A traction converter on a modern electric locomotive or EMU, using power electronics, primarily allows:
- A. Elimination of the need for any transformer
- B. Direct mechanical coupling between wheels with no electrical link
- C. Generation of the 25kV supply from the wheels
- D. Variable voltage/variable frequency control of the traction motors for smooth speed and torque control
Answer: Variable voltage/variable frequency control of the traction motors for smooth speed and torque control
Explanation: Variable voltage/variable frequency control of the traction motors for smooth speed and torque control — verified fact for Railway Electrical Engineering Group B LDCE.
127. The distributed traction concept in EMUs (multiple powered axles across the rake) generally provides the benefit of:
- A. Elimination of the need for any electrical supply
- B. Better acceleration and adhesion utilization suited to frequent-stop suburban services
- C. Guaranteed zero maintenance for the life of the train
- D. Automatic elimination of braking systems
Answer: Better acceleration and adhesion utilization suited to frequent-stop suburban services
Explanation: Better acceleration and adhesion utilization suited to frequent-stop suburban services — verified fact for Railway Electrical Engineering Group B LDCE.
128. A motor coach in an EMU/MEMU rake typically carries which key traction-related electrical equipment underslung or onboard?
- A. Traction motors and associated control/converter equipment for that unit
- B. Only the train's toilets and no electrical gear
- C. Only passenger seating with zero electrical equipment
- D. Only luggage storage racks
Answer: Traction motors and associated control/converter equipment for that unit
Explanation: Traction motors and associated control/converter equipment for that unit — verified fact for Railway Electrical Engineering Group B LDCE.
129. MEMU (Mainline Electric Multiple Unit) trains are generally designed for:
- A. Operation without any electrical traction equipment
- B. Only long-distance non-stop freight haulage
- C. Suburban/mainline passenger service with frequent stops, using distributed electric traction similar in concept to EMUs but for longer mainline routes
- D. Operation exclusively on non-electrified diesel routes
Answer: Suburban/mainline passenger service with frequent stops, using distributed electric traction similar in concept to EMUs but for longer mainline routes
Explanation: Suburban/mainline passenger service with frequent stops, using distributed electric traction similar in concept to EMUs but for longer mainline routes — verified fact for Railway Electrical Engineering Group B LDCE.
130. EMU (Electric Multiple Unit) trains differ from a locomotive-hauled train mainly in that EMUs have:
- A. No electrical system at all, relying only on gravity
- B. A single traction motor for the entire rake located in the last coach only
- C. Traction motors and equipment distributed across multiple coaches/cars rather than concentrated in one separate locomotive
- D. No pantograph, drawing power only from batteries
Answer: Traction motors and equipment distributed across multiple coaches/cars rather than concentrated in one separate locomotive
Explanation: Traction motors and equipment distributed across multiple coaches/cars rather than concentrated in one separate locomotive — verified fact for Railway Electrical Engineering Group B LDCE.
131. End-on generation (EOG), historically common before wider HOG adoption, typically relied on:
- A. Battery power alone for the entire journey
- B. The locomotive's main traction transformer directly with no separate car
- C. Solar panels mounted on the coach roof
- D. A separate generator car (power car) supplying electricity to the rake of coaches
Answer: A separate generator car (power car) supplying electricity to the rake of coaches
Explanation: A separate generator car (power car) supplying electricity to the rake of coaches — verified fact for Railway Electrical Engineering Group B LDCE.
132. Head-on generation (HOG) power supply for passenger coaches refers to the arrangement where:
- A. Coaches run without any electrical supply at all
- B. Each coach generates power using its own diesel generator regardless of the locomotive
- C. Power is drawn only from a separate power car with no locomotive contribution ever
- D. Electrical power for coach lighting, fans, and air-conditioning is drawn from the locomotive itself rather than individual coach generators
Answer: Electrical power for coach lighting, fans, and air-conditioning is drawn from the locomotive itself rather than individual coach generators
Explanation: Electrical power for coach lighting, fans, and air-conditioning is drawn from the locomotive itself rather than individual coach generators — verified fact for Railway Electrical Engineering Group B LDCE.
133. Auxiliary power supply systems on a locomotive/coach are responsible for supplying power to loads such as:
- A. Only the pantograph's mechanical raising mechanism
- B. Only the traction substation's transformer
- C. Compressors, fans, lighting, and other onboard equipment other than the main traction motors
- D. Only the OHE contact wire heating
Answer: Compressors, fans, lighting, and other onboard equipment other than the main traction motors
Explanation: Compressors, fans, lighting, and other onboard equipment other than the main traction motors — verified fact for Railway Electrical Engineering Group B LDCE.
134. Rheostatic braking on an electric locomotive dissipates the generated braking energy mainly through:
- A. Feeding it back into the OHE in all cases without exception
- B. Resistor banks that convert the electrical energy into heat, which is then dissipated
- C. Converting it into compressed air only
- D. Storing it permanently in an onboard battery in all locomotives
Answer: Resistor banks that convert the electrical energy into heat, which is then dissipated
Explanation: Resistor banks that convert the electrical energy into heat, which is then dissipated — verified fact for Railway Electrical Engineering Group B LDCE.
135. Compared to purely rheostatic (resistive) braking, regenerative braking offers the real advantage of:
- A. Increasing the train's top speed
- B. Eliminating the need for any friction brakes on the train
- C. Recovering and reusing braking energy instead of dissipating it entirely as heat
- D. Requiring no electrical or mechanical components at all
Answer: Recovering and reusing braking energy instead of dissipating it entirely as heat
Explanation: Recovering and reusing braking energy instead of dissipating it entirely as heat — verified fact for Railway Electrical Engineering Group B LDCE.
136. Electrical energy produced during regenerative braking of a train can, where the system supports it, be:
- A. Immediately destroyed with no possible use
- B. Converted into diesel fuel
- C. Used only to power station lighting via a direct wire link with no conversion needed
- D. Fed back into the OHE for use by other trains drawing power nearby
Answer: Fed back into the OHE for use by other trains drawing power nearby
Explanation: Fed back into the OHE for use by other trains drawing power nearby — verified fact for Railway Electrical Engineering Group B LDCE.
137. Regenerative braking on an electric locomotive works on the principle that the traction motor, during braking, is made to function as a:
- A. Generator, converting the train's kinetic energy back into electrical energy
- B. Signal transmitter for the next station
- C. Heater for the driver's cab
- D. Air compressor for the brake system
Answer: Generator, converting the train's kinetic energy back into electrical energy
Explanation: Generator, converting the train's kinetic energy back into electrical energy — verified fact for Railway Electrical Engineering Group B LDCE.
138. Older-generation DC traction motors used in some legacy electric locomotives required more maintenance mainly because of their:
- A. Their operation without any electrical current
- B. Complete absence of any moving parts
- C. Their use of three-phase supply only
- D. Brushes and commutator, which wear over time and need periodic servicing
Answer: Brushes and commutator, which wear over time and need periodic servicing
Explanation: Brushes and commutator, which wear over time and need periodic servicing — verified fact for Railway Electrical Engineering Group B LDCE.
139. Three-phase induction motors are widely used as traction motors in modern electric locomotives mainly due to their advantage of:
- A. Eliminating the need for any onboard transformer
- B. Being simpler than a DC motor in every historical era
- C. Requiring no electrical supply at all
- D. Robustness, lower maintenance (no brushes/commutator), and good control characteristics when fed via variable-frequency drives
Answer: Robustness, lower maintenance (no brushes/commutator), and good control characteristics when fed via variable-frequency drives
Explanation: Robustness, lower maintenance (no brushes/commutator), and good control characteristics when fed via variable-frequency drives — verified fact for Railway Electrical Engineering Group B LDCE.
140. After the onboard transformer steps down the voltage, a modern AC electric locomotive typically uses power electronic converters mainly to:
- A. Replace the pantograph function entirely
- B. Generate the initial 25kV traction supply
- C. Convert and regulate the supply (e.g. AC to DC, then DC to variable-frequency AC) to control traction motor speed and torque
- D. Directly cool the locomotive cab
Answer: Convert and regulate the supply (e.g. AC to DC, then DC to variable-frequency AC) to control traction motor speed and torque
Explanation: Convert and regulate the supply (e.g. AC to DC, then DC to variable-frequency AC) to control traction motor speed and torque — verified fact for Railway Electrical Engineering Group B LDCE.
141. In a modern electric locomotive running on 25kV AC supply, the onboard main transformer's primary role is to:
- A. Generate the 25kV supply itself
- B. Provide compressed air for braking
- C. Convert mechanical energy into electrical energy
- D. Step down the 25kV pantograph supply to a lower voltage suitable for the traction converter/motor circuits
Answer: Step down the 25kV pantograph supply to a lower voltage suitable for the traction converter/motor circuits
Explanation: Step down the 25kV pantograph supply to a lower voltage suitable for the traction converter/motor circuits — verified fact for Railway Electrical Engineering Group B LDCE.
142. Filters are sometimes installed in traction substations mainly to address:
- A. Track alignment issues
- B. Ticket booking errors
- C. Harmonic currents/voltages generated by non-linear traction loads, improving power quality
- D. Signal aspect failures
Answer: Harmonic currents/voltages generated by non-linear traction loads, improving power quality
Explanation: Harmonic currents/voltages generated by non-linear traction loads, improving power quality — verified fact for Railway Electrical Engineering Group B LDCE.
143. Harmonic distortion in traction power supply can arise mainly due to:
- A. The height of the OHE masts
- B. Perfectly linear resistive loads only
- C. Non-linear loads such as power-electronic converters used in modern locomotives
- D. The colour of the insulators used
Answer: Non-linear loads such as power-electronic converters used in modern locomotives
Explanation: Non-linear loads such as power-electronic converters used in modern locomotives — verified fact for Railway Electrical Engineering Group B LDCE.
144. Reactive power in an AC traction system is generally associated with:
- A. The total useful energy delivered to move the train
- B. Energy stored permanently in the rails
- C. Energy that oscillates between source and inductive/capacitive elements without doing net useful work
- D. Energy consumed only by lighting circuits
Answer: Energy that oscillates between source and inductive/capacitive elements without doing net useful work
Explanation: Energy that oscillates between source and inductive/capacitive elements without doing net useful work — verified fact for Railway Electrical Engineering Group B LDCE.
145. A key operational difference between a fuse and a circuit breaker is that a circuit breaker:
- A. Can be reset and reused after tripping, whereas a blown fuse must be physically replaced
- B. Cannot interrupt any fault current
- C. Always costs less than a fuse
- D. Can never be reset under any circumstance
Answer: Can be reset and reused after tripping, whereas a blown fuse must be physically replaced
Explanation: Can be reset and reused after tripping, whereas a blown fuse must be physically replaced — verified fact for Railway Electrical Engineering Group B LDCE.
146. A fuse used for protecting low-power auxiliary circuits operates by:
- A. Automatically resetting itself after tripping, like a circuit breaker
- B. Increasing the voltage during a fault
- C. Melting and breaking the circuit when current exceeds its rated value for a sufficient time
- D. Storing electrical energy for later use
Answer: Melting and breaking the circuit when current exceeds its rated value for a sufficient time
Explanation: Melting and breaking the circuit when current exceeds its rated value for a sufficient time — verified fact for Railway Electrical Engineering Group B LDCE.
147. A key reason substations maintain a stock of spare relays, fuses, and breakers is to:
- A. Minimize downtime by allowing quick replacement of a failed protective device
- B. Replace the need for periodic maintenance entirely
- C. Reduce the number of trains scheduled
- D. Increase the traction voltage during peak hours
Answer: Minimize downtime by allowing quick replacement of a failed protective device
Explanation: Minimize downtime by allowing quick replacement of a failed protective device — verified fact for Railway Electrical Engineering Group B LDCE.
148. Regular thermal scanning (thermography) of substation equipment such as busbar joints is done mainly to detect:
- A. The exact train timetable for the day
- B. Track gauge deviations
- C. The colour scheme of the substation building
- D. Loose connections or overheating hotspots before they develop into a serious fault
Answer: Loose connections or overheating hotspots before they develop into a serious fault
Explanation: Loose connections or overheating hotspots before they develop into a serious fault — verified fact for Railway Electrical Engineering Group B LDCE.
149. A neutral earthing resistor/reactor, where used in a power system, is intended to:
- A. Eliminate the need for any transformer
- B. Increase fault current to the maximum possible value
- C. Limit the magnitude of earth fault current to a safer, more controllable level
- D. Directly power the traction motors
Answer: Limit the magnitude of earth fault current to a safer, more controllable level
Explanation: Limit the magnitude of earth fault current to a safer, more controllable level — verified fact for Railway Electrical Engineering Group B LDCE.
150. In electrical protection terminology, 'discrimination' between protective devices refers to:
- A. Deciding train ticket pricing during peak season
- B. Selecting which staff member operates a switch
- C. Ensuring the protective device closest to a fault operates first, before upstream devices, to minimize the extent of disconnection
- D. Choosing which locomotive gets priority on the track
Answer: Ensuring the protective device closest to a fault operates first, before upstream devices, to minimize the extent of disconnection
Explanation: Ensuring the protective device closest to a fault operates first, before upstream devices, to minimize the extent of disconnection — verified fact for Railway Electrical Engineering Group B LDCE.
151. An interlock between an isolator and its associated circuit breaker is provided mainly to:
- A. Eliminate the need for the circuit breaker altogether
- B. Prevent the isolator from being opened while the circuit breaker is still closed and carrying load current, avoiding a dangerous arc
- C. Increase the traction voltage supplied to the isolator
- D. Allow the isolator to generate power independently
Answer: Prevent the isolator from being opened while the circuit breaker is still closed and carrying load current, avoiding a dangerous arc
Explanation: Prevent the isolator from being opened while the circuit breaker is still closed and carrying load current, avoiding a dangerous arc — verified fact for Railway Electrical Engineering Group B LDCE.
152. Insulation resistance testing (e.g. using a megger) on electrical equipment/cables is performed mainly to check:
- A. The exact position of the pantograph
- B. The health of the insulation, to catch deterioration before it leads to a fault
- C. The signalling aspect displayed at the next station
- D. The train's average speed on that section
Answer: The health of the insulation, to catch deterioration before it leads to a fault
Explanation: The health of the insulation, to catch deterioration before it leads to a fault — verified fact for Railway Electrical Engineering Group B LDCE.
153. An earthing mat or grid installed at a substation is designed primarily to:
- A. Provide a walking surface with no electrical function
- B. Increase the substation's transformer capacity
- C. Generate backup electrical power during outages
- D. Equalize ground potential across the substation area, limiting dangerous step and touch voltages during a fault
Answer: Equalize ground potential across the substation area, limiting dangerous step and touch voltages during a fault
Explanation: Equalize ground potential across the substation area, limiting dangerous step and touch voltages during a fault — verified fact for Railway Electrical Engineering Group B LDCE.
154. An overhead traction supply system's protection scheme is generally designed with selective/graded relay settings mainly so that:
- A. No breaker ever trips regardless of fault severity
- B. The traction voltage is automatically doubled after any fault
- C. All breakers on the entire network trip simultaneously for any fault anywhere
- D. Only the breaker nearest to a fault trips, isolating the smallest possible section and minimizing disruption
Answer: Only the breaker nearest to a fault trips, isolating the smallest possible section and minimizing disruption
Explanation: Only the breaker nearest to a fault trips, isolating the smallest possible section and minimizing disruption — verified fact for Railway Electrical Engineering Group B LDCE.
155. The neutral point of a star-connected transformer winding, when earthed, primarily helps in:
- A. Increasing the transformer's power rating permanently
- B. Providing a reference/return path and enabling detection of earth faults
- C. Eliminating the need for any circuit breaker
- D. Directly powering the locomotive's traction motors
Answer: Providing a reference/return path and enabling detection of earth faults
Explanation: Providing a reference/return path and enabling detection of earth faults — verified fact for Railway Electrical Engineering Group B LDCE.
156. A lightning/surge arrester connected near substation equipment operates by:
- A. Providing a low-impedance path to earth for a voltage surge once it exceeds a set threshold, then reverting to a high-impedance state in normal operation
- B. Increasing the transformer's turns ratio during a surge
- C. Permanently short-circuiting the line at all times
- D. Generating extra voltage during a storm
Answer: Providing a low-impedance path to earth for a voltage surge once it exceeds a set threshold, then reverting to a high-impedance state in normal operation
Explanation: Providing a low-impedance path to earth for a voltage surge once it exceeds a set threshold, then reverting to a high-impedance state in normal operation — verified fact for Railway Electrical Engineering Group B LDCE.
157. Periodic testing of transformer oil (such as dielectric strength testing) is carried out mainly to:
- A. Calculate the locomotive's fuel efficiency
- B. Measure the train's punctuality
- C. Assess the oil's insulating condition and detect early signs of deterioration or contamination
- D. Determine the OHE's mechanical tension
Answer: Assess the oil's insulating condition and detect early signs of deterioration or contamination
Explanation: Assess the oil's insulating condition and detect early signs of deterioration or contamination — verified fact for Railway Electrical Engineering Group B LDCE.
158. Transformer oil in a traction substation transformer primarily serves the dual purpose of:
- A. Replacing the need for a core entirely
- B. Acting as the primary conductor of current
- C. Providing electrical insulation and dissipating heat generated by the windings
- D. Generating additional voltage and carrying signalling data
Answer: Providing electrical insulation and dissipating heat generated by the windings
Explanation: Providing electrical insulation and dissipating heat generated by the windings — verified fact for Railway Electrical Engineering Group B LDCE.
159. Buchholz relays, commonly fitted on oil-filled power transformers, are designed to detect:
- A. Track circuit failures
- B. Overspeed of the locomotive
- C. Incorrect signal aspects
- D. Gas accumulation or oil surges within the transformer tank caused by internal faults
Answer: Gas accumulation or oil surges within the transformer tank caused by internal faults
Explanation: Gas accumulation or oil surges within the transformer tank caused by internal faults — verified fact for Railway Electrical Engineering Group B LDCE.
160. A differential protection scheme, where used on a transformer, is designed to detect faults by comparing:
- A. Current entering and leaving the protected equipment; a significant mismatch indicates an internal fault
- B. The number of trains passing per hour
- C. The colour of the transformer oil only
- D. The ambient temperature outside the substation
Answer: Current entering and leaving the protected equipment; a significant mismatch indicates an internal fault
Explanation: Current entering and leaving the protected equipment; a significant mismatch indicates an internal fault — verified fact for Railway Electrical Engineering Group B LDCE.
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