Electric Illumination MCQs

61. The level of illumination from a 100 W incandescent lamp will not increase by

(A) increasing the supply voltage
(B) increasing filament temperature
(C) increasing glass shell diameter.

Answer. C

62. The rate of evaporation of tungsten filament in a lamp depends on

(A) glass shell diameter
(B) exhaust tube diameter
(C) vapor pressure inside
(D) none of the above.

Answer. C

63. A gas filled filament bulbs, the gas used is

(A) oxygen
(B) helium
(C) nitrogen
(D) ozone.

Answer. C

64. Heat from the filament of a lamp is transmitted to the surrounding mainly through

(A) conduction
(B) convection
(C) radiation

Answer. C

65. In a fluorescent tube circuit, choke acts as

(A) starter
(B) power factor improving device
(C) source of heat
(D) current limiting device.

Answer. D

66. When a fluorescent lamp is to be operated on dc which of the following additional device must be incorporated in the circuit?

(A) Condenser
(B) Transformer
(C) Resistance
(D) Inductance

Answer. C

67. For same rating the amount of radiant heat produced in which of the following lamp is the least?

(A) Fluorescent lamp
(B) Filament lamp
(C) Sodium vapor lamp
(D) Mercury vapor lamp

Answer. A

68. The amount of radiant heat produced by a fluorescent lamp is nearly what percent of that of a filament lamp of same rating

(A) 80%
(B) 60%
(C) 40%
(D) 20%

Answer. D

69. Which of the following lamp gives nearly ultra-violet light?

(A) Vacuum type filament lamp
(B) Nitrogen filed filament lamp
(C) Argon filled filament lamp
(D) Carbon arc lamp.

Answer. D

70. Luminous flux is

(A) rate of energy radiation in the form of light waves
(B) light energy radiated by sun
(C) part of light energy, radiated by sun which is received on earth
(D) none of the above.

Answer. A

71. Match the following

        Column I                         Column II

(a) Luminous flux         (i) Candela
(b) Luminous                 (ii) Candle power x intensity Solid angle
(c) Lumen                       (iii) Lumens/W steredians
(d)Candle power           (iv) Lumens.

(A) a-(i), b-(ii), c-(iii),d-(iv)
(B) a-(iv), b-(i), c-(ii), d-(iii)
(C) a-(i), b-(iv), c-(ii), d-(iii)
(D) a – (iv), b – (iii), c- (i), d – (ii)

Answer. B

72. According to Lambert’s law, the illumination on a surface is proportional to

(A) cos2θ
(B) cos3θ
(C) 1/cos3θ
(D) 1/ cos2θ

Answer. B

73. A lamp has a mean spherical candle power of 25, the total flux of light from the lamp is

(A) 25 lumens
(B) 25 π lumens
(C) 314 lumens
(D) 625 lumens.

Answer. C

74. Which of the following material can be used for the filaments in incandescent lamps is

(A) carbon
(B) tungsten
(C) tantalum
(D) any of the above.

Answer. D

75. The melting point of carbon is

(A) 1800°C
(B) 2200°C
(C) 3500°C
(D) 5500° C.

Answer. C

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