Electrical Power Engineering Multiple Choice Questions and Answers (MCQs) Part 8:

352. The luminous efficiency of a sodium vapour lamp is ………… lumens per watt.

(a) 40-50
(b) 50-100
(c) 120-200
(d) 10-12

Answer : (a) 40-50


353. Phosphor zinc silicate produces light of

(a) pink colour.
(b) green colour.
(c) red colour.
(d) yellow colour.

Answer : (b) green colour.


354. A mercury vapour lamp gives light of

(a) pink colour.
(b) yellow colour.
(c) greenish-blue colour.
(d) red colour.

Answer : (c) greenish-blue colour.


355. High pressure mercury vapour lamps

(a) are similar in construction to sodium vapour lamps.
(b) need 4 or 5 minutes to attain full brilliancy.
(c) are generally used for general industrial lighting, railway yards, work areas, shoping centres etc.
(d) all of the above.

Answer : (d) all of the above.


356. In high pressure mercury vapour lamps

(a) the main electrodes are made of tungsten wire in the form of helix.
(b) the choke is provided to limit the current to a safe value.
(c) in addition to two main electrodes a starting (auxiliary) elec­trode is connected through a high resistance.
(d) all of the above.

Answer : (d) all of the above.


357. The luminous efficiency of high pressure mercury vapour lamps ranges from ……… lumens per watt.

(a) 30 to 40
(b) 60 to 100
(c) 100 to 150
(d) 250 to 400

Answer : (a) 30 to 40


358. In mercury iodide lamps

(a) a number of iodides are added, in addition to mercury, to fill up the gaps in the light spectrum.
(b) a separate ignition device, in addition to the choke, is pro­vided.
(c) both (a) and (b).
(d) none of the above.

Answer : (c) both (a) and (b).


359. Mercury iodide lamps

(a) are similar in construction to high pressure mercury vapour lamps.
(b) have luminous efficiency of the order of 80 lumens per watt.
(c) are suitable for applications in the field of floodlighting, in­dustrial lighting and public lighting.
(d) all of the above.

Answer : (d) all of the above.


360. Which of the following lamps is a cold cathode lamp ?

(a) Sodium vapour lamp.
(b) Neon lamp.
(c) Mercury vapour lamp.
(d) None of the above.

Answer : (b) Neon lamp.


361. Neon lamps

(a) are of the size of ordinary incandescent lamps.
(b) have power consumption of the order of 5 watts.
(c) are used as indicator lamps, night lamps, for determination of polarity of dc mains.
(d) all of the above.

Answer : (d) all of the above.


362. In neon signs argon gas is used to give

(a) red colour.
(b) blue colour.
(c) pink colour.
(d) green colour.

Answer : (a) red colour.


363. In neon signs, neon with a mixture of mercury is used to give

(a) blue colour.
(b) green colour.
(c) pink colour.
(d) yellow colour.

Answer : (b) green colour.


364. The electrodes of neon tube work at

(a) very low temperatures.
(b) ordinary voltage.
(c) 2 kV to 6 kV.
(d) 33 kV.

Answer : (c) 2 kV to 6 kV.


365. Neon tubes are widely used for

(a) advertising.
(b) indoor lighting.
(c) road signaling.
(d) airport lighting.

Answer : (a) advertising.


366. The vapour discharge tube used for domestic light has

(a) one filament.
(b) two filaments.
(c) four filaments.
(d) no filament.

Answer : (b) two filaments.


367. The fluorescent tube is coated from inside with a thin layer of fluorescent material in the form of powder in order to

(a) absorb invisible ultraviolet rays and radiate visible rays.
(b) improve the appearance.
(c) reduce glare.
(d) improve life.

Answer : (a) absorb invisible ultraviolet rays and radiate visible rays.


368. A stabilising choke is connected in the fluorescent tube circuit so as to

(a) reduce the flicker.
(b) act as a ballast in operating conditions and provide a voltage impulse for starting.
(c) act as a starter.
(d) avoid radio-interference.

Answer : (b) act as a ballast in operating conditions and provide a voltage impulse for starting.


369. A capacitor is connected across the fluorescent tube circuit in order to

(a) eliminate the noise.
(b) limit the current.
(c) improve the power factor of the tube circuit.
(d) all of the above.

Answer : (c) improve the power factor of the tube circuit.


370. Which of the following is present inside the fluorescent tube ?

(a) Helium and oxygen.
(b) Argon and neon.
(c) Argon and carbon dioxide.
(d) Mercury vapour.

Answer : (d) Mercury vapour.


371. In a fluorescent tube, a ballast resistance is connected in series with the choke

(a) when the tube is operated on dc supply.
(b) when the tube is operated on ac supply.
(c) to reduce radio-interference.
(d) to reduce stroboscopic effects.

Answer : (a) when the tube is operated on dc supply.


372. For operation of fluorescent tube on dc supply the additional de­vice incorporated in the tube circuit is a

(a) transformer.
(b) resistor.
(c) inductor.

Answer : (b) resistor.


373. The light of fluorescent tube appears cooler than that from an incandescent lamp. This is due to the fact that

(a) the tube consumes less power.
(b) surface area of tube is larger than that of the incandescent lamp.
(c) tungsten is not used in the tube.
(d) none of the above.

Answer : (c) tungsten is not used in the tube.


374. Sometimes the wheels of the rotating machinery, in fluorescent tube lighting, appear to be stationary . This is due to

(a) luminescence effect.
(b) light fluctuations.
(c) stroboscopic effect.
(d) all of the above.

Answer : (c) stroboscopic effect.


375. The flicker effect of fluorescent lamps is more pronounced at

(a) lower voltages.
(b) higher voltages.
(c) higher frequencies.
(d) lower frequencies.

Answer : (d) lower frequencies.


376. The frequency of flickers in a fluorescent tube operating at 220 V, 50 Hz supply is

(a) 200 per second.
(b) 100 per second.
(c) 50 per second.
(d) 25 per second.

Answer : (b) 100 per second.


377. Standard wattage of a 1 m fluorescent tube is

(a) 25 W
(b) 65 W
(c) 80 W
(d) 100 W

Answer : (a) 25 W


378. A fluorescent tube can be operated on

(a) both dc as well as ac.
(b) ac only.
(c) dc only.
(d) satisfactorily only on dc.

Answer : (a) both dc as well as ac.


379. Radio-interference from a fluorescent tube can be reduced by

(a) eliminating choke.
(b) connecting a small capacitor across starter terminals.
(c) putting two tubes in parallel.
(d) any of the above.

Answer : (b) connecting a small capacitor across starter terminals.


380. In a mercury vapour lamp light, red objects appear black. This is on account of

(a) colour mixing.
(b) high wavelengths of red colour.
(c) absence of red light from lamp radiations.
(d) absorption of red light by the lamp.

Answer : (c) absence of red light from lamp radiations.


381. Blinking of a fluorescent tube may be on account of

(a) low circuit voltage.
(b) loose contact.
(c) defective starter.
(d) any of the above.

Answer : (d) any of the above.


382. The cost of a fluorescent tube is more than that of an incandescent lamp on account of

(a) more components in the tube.
(b) more quantity of glass in the tube.
(c) more labour required.
(d) all of the above.

Answer : (d) all of the above.


383. The life of a fluorescent tube is affected by

(a) low voltage.
(b) high voltage.
(c) frequency of switching and blinking.
(d) all of the above.

Answer : (d) all of the above.


384. The disadvantage(s) of fluorescent tubes in comparison to fila­ment lamps is/are

(a) high cost.
(b) noise in choke.
(c) stroboscopic effect.
(d) all of the above.

Answer : (d) all of the above.


385. The ratio of radiant heat produced by a fluorescent tube and that by a filament lamp of the same rating is

(a) 0.2
(b) 0.35
(c) 0.6
(d) 0.75

Answer : (a) 0.2


386. The lamp that cannot sustain much voltage fluctuations is

(a) sodium vapour lamp.
(b) mercury vapour lamp.
(c) incandescent lamp.
(d) mercury iodide lamp.

Answer : (c) incandescent lamp.


387. The lamp that gives nearly ultraviolet light is

(a) carbon arc lamp.
(b) vacuum type filament lamp.
(c) argon gas filled filament lamp.
(d) all of the above.

Answer : (a) carbon arc lamp.


388. For the same wattage the cheapest lamp is

(a) sodium vapour lamp.
(b) GLS lamp.
(c) halogen lamp.
(d) fluorescent tube.

Answer : (b) GLS lamp.


389. Power factor is highest in case of

(a) sodium vapour lamp.
(b) mercury vapour lamp.
(c) incandescent lamp.
(d) neon lamp.

Answer : (c) incandescent lamp.


390. The lamp which gives nearly monochromatic light is

(a) sodium vapour lamp.
(b) mercury vapour lamp.
(c) tungsten filament lamp.
(d) fluorescent tube.

Answer : (a) sodium vapour lamp.


391. The lamp that does not have separate choke is

(a) mercury vapour lamp.
(b) sodium vapour lamp.
(c) fluorescent tube.
(d) all of the above.

Answer : (b) sodium vapour lamp.


392. For the same wattage the lamp that will produce minimum radiant heat is

(a) sodium vapour lamp.
(b) fluorescent lamp.
(c) tungsten filament lamp.
(d) mercury vapour lamp.

Answer : (b) fluorescent lamp.


393. The lamp/tube preferred for air-conditioned spaces is

(a) sodium vapour lamp.
(b) mercury vapour lamp.
(c) fluorescent tube.
(d) GLS lamp.

Answer : (c) fluorescent tube.


394. The lamp that causes radio-interference is

(a) fluorescent tube.
(b) halogen lamp.
(c) mercury vapour lamp.
(d) all of the above.

Answer : (a) fluorescent tube.


395. The lamp that cannot be used for dimming is

(a) cold cathode lamp.
(b) fluorescent lamp.
(c) GLS lamp.
(d) all of the above.

Answer : (b) fluorescent lamp.


396. Which of the following application does not require ultraviolet lamps ?

(a) Aircraft cockpit dashboard lighting.
(b) Blue print machines.
(c) Car lighting.
(d) None of the above.

Answer : (c) Car lighting.


397. Floodlighting is not used for

(a) industrial purposes.
(b) advertising purposes.
(c) aesthetic purposes.
(d) any of the above.

Answer : (a) industrial purposes.


398. The lumens emitted from a 100 W incandescent lamp will not increase if

(a) supply voltage is increased.
(b) filament temperature is increased.
(c) the diameter of the glass shell is increased.
(d) any of the above.

Answer : (c) the diameter of the glass shell is increased.


399. Total flux required in any lighting scheme depends inversely on

(a) surface area.
(b) space-height ratio.
(c) illumination.
(d) coefficient of utilisation.

Answer : (b) space-height ratio.


400. To avoid glare

(a) object should be viewed from a distance.
(b) object should be moved constantly.
(c) object should be viewed from a close vicinity.
(d) viewer should move constantly.

Answer : (a) object should be viewed from a distance.


401. The illumination level on a surface is least affected by

(a) candle power of light source.
(b) ambient temperature.
(c) type of reflector used.
(d) distance of the light source.

Answer : (b) ambient temperature.

Scroll to Top