27 real Illumination & Utilization questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Lumen and lux?
Junior
A.lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
B.eddy currents induced by a high-frequency coil heat a conductive workpiece from within, with depth set by skin effect
C.luminous flux is measured in lumens; illuminance in lux equals lumens received per square metre of surface
D.motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
A.Lumen and lux — lighting design formula N = E·A/(F·UF·MF) giving the number of luminaires from required lux, area, utilisation and maintenance factors
B.Lumen and lux — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
C.Lumen and lux — luminous flux is measured in lumens; illuminance in lux equals lumens received per square metre of surface
D.Lumen and lux — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
A.Inverse square law of illumination — stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed
B.Inverse square law of illumination — illuminance on a surface normal to the light falls with the square of its distance from a point source
C.Inverse square law of illumination — heating of a non-conductive material by dielectric loss in a 10–30 MHz electric field, used for wood, plastics and food
D.Inverse square law of illumination — lighting design formula N = E·A/(F·UF·MF) giving the number of luminaires from required lux, area, utilisation and maintenance factors
A.Luminous efficacy — illuminance on a surface normal to the light falls with the square of its distance from a point source
B.Luminous efficacy — stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed
C.Luminous efficacy — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
D.Luminous efficacy — eddy currents induced by a high-frequency coil heat a conductive workpiece from within, with depth set by skin effect
11. Which term means: "lighting design formula N = E·A/(F·UF·MF) giving the number of luminaires from required lux, area, utilisation and maintenance factors"?
A.Lumen method — stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed
B.Lumen method — lighting design formula N = E·A/(F·UF·MF) giving the number of luminaires from required lux, area, utilisation and maintenance factors
C.Lumen method — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
D.Lumen method — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
A.Induction heating — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
B.Induction heating — force at the wheel rim needed to accelerate a train and overcome gradient and track resistance over a trapezoidal speed-time curve
C.Induction heating — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
D.Induction heating — eddy currents induced by a high-frequency coil heat a conductive workpiece from within, with depth set by skin effect
A.Dielectric heating — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
B.Dielectric heating — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
C.Dielectric heating — eddy currents induced by a high-frequency coil heat a conductive workpiece from within, with depth set by skin effect
D.Dielectric heating — heating of a non-conductive material by dielectric loss in a 10–30 MHz electric field, used for wood, plastics and food
20. Which term means: "force at the wheel rim needed to accelerate a train and overcome gradient and track resistance over a trapezoidal speed-time curve"?
A.Tractive effort — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
B.Tractive effort — force at the wheel rim needed to accelerate a train and overcome gradient and track resistance over a trapezoidal speed-time curve
C.Tractive effort — lighting design formula N = E·A/(F·UF·MF) giving the number of luminaires from required lux, area, utilisation and maintenance factors
D.Tractive effort — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
23. Which term means: "stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed"?
A.Star-delta starting — lumens emitted per watt consumed, roughly 10–15 for incandescent, 60–100 for fluorescent and 100–200 for LED lamps
B.Star-delta starting — stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed
C.Star-delta starting — force at the wheel rim needed to accelerate a train and overcome gradient and track resistance over a trapezoidal speed-time curve
D.Star-delta starting — eddy currents induced by a high-frequency coil heat a conductive workpiece from within, with depth set by skin effect
26. Which term means: "motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage"?
A.Four-quadrant drive operation — stator connected in star at start, cutting line current and torque to one-third of direct-on-line values, then switched to delta near rated speed
B.Four-quadrant drive operation — illuminance on a surface normal to the light falls with the square of its distance from a point source
C.Four-quadrant drive operation — heating of a non-conductive material by dielectric loss in a 10–30 MHz electric field, used for wood, plastics and food
D.Four-quadrant drive operation — motor runs in forward and reverse motoring and forward and reverse braking, needing a converter that can reverse both current and voltage
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