Electric Illumination MCQ PDF

21. Heat from the lamp filament is transmitted to the surrounding mainly through

(a) circulation.
(b) conduction
(c) convection.
(d) radiation.

22. Which of the following material is most commonly used for the filaments in incandescent lamps ?

(a) Tungsten.
(b) Osmium.
(c) Tantalum.
(d) Silver.

23. A zero watt incandescent lamp consumes power of

(a) zero watt.
(b) 5 – 10 W.
(c) about 15 W.
(d) about 25 W.

24. The safe operating temperature of a tungsten filament lamp is

(a) 1,000°C
(b) 2,000°C
(c) 3,000°C
(d) 3,500°C

25. The output of a tungsten filament depends on

(a) size of the shell.
(b) size of the lamp.
(c) temperature of filament.
(d) all of the above.

27. What percentage of the input energy is radiated by filament lamps ?

(a) 60 – 70 per cent.
(b) 40 – 50 per cent.
(c) 25 – 30 per cent.
(d) 10 – 15 per cent.

28. An electric bulb, when broken, produces bang. It is on account of

(a) vacuum inside the bulb.
(b) pressure inside is equal to that outside.
(c) pressure of air in the bulb.
(d) none of the above.

29. In an incandescent lamp, bird cage filament is usually used in vacuum bulb so as to

(a) increase the life span of the filament.
(b) give uniform radiations.
(c) reduce the oxidation phenomenon.
(d) reduce the convection losses.

30. Filament lamps normally operate at a power factor of

(a) 0.5 lagging.
(b) 0.8 lagging.
(c) unity.
(d) 0.85 leading.

31. Most affected parameter of a filament lamp due to variation in operating voltage is

(a) life.
(b) light output.
(c) luminous efficiency.
(d) wattage.

32. The lumens output of an incandescent lamp with the variation in operating voltage is given as lumens output α Vⁿ where n is a constant. The value of n for tungsten is

(a) from 1.0 to 2.2
(b) from 3 to 4
(c) from 8 to 10
(d) from 10 to 12

33. Which gas is sometimes used in filament lamps ?

(a) Nitrogen.
(b) Carbon dioxide.
(c) Argon.
(d) Krypton.

34. Which of the following vapor/gas will give yellow color in a filament lamp ?

(a) Helium.
(b) Mercury.
(c) Magnesium.
(d) Sodium.

35. Magnesium vapor in a filament lamp gives

(a) green color light.
(b) pink color light.
(c) blue color light.
(d) white color light.

36. The gas used in a gas-filled filament lamp is

(a) helium.
(b) oxygen.
(c) nitrogen.
(d) ozone.

37. In filament lamps, coiled coil filaments are used in

(a) colored lamps.
(b) gas-filled lamps.
(c) low wattage lamps.
(d) higher wattage lamps.

38. In electric discharge lamps light is produced by

(a) magnetic effect of current.
(b) heating effect of current.
(c) cathode ray emission.
(d) ionization in a gas or vapor.

39. In electric discharge lamps for stabilization of arc

(a) a choke is connected in series with the supply.
(b) a variable resistance is connected in series with the circuit.
(c) a condenser is connected across the supply.
(d) any of the above.

40. Glow lamps

(a) have hot cathode.
(b) have cold cathode.
(c) draw more power.
(d) cannot withstand shocks.