Electric Illumination MCQs

31. The life of incandescent lamp is expected to be

(A) 100 hours
(B) 200 hours
(C) 1000 hours
(D) 10000 hours

Answer
Answer. C

32. The source of illumination for a cinema projector is

(A) Incandescent lamp
(B) Mercury vapor lamp
(C) Sodium lamp
(D) Carbon arc lamp.

Answer
Answer. D

33. Sodium vapor lamps need ionization potential of about

(A) 5 volts
(B) 50 volts
(C) 100 volts
(D) 112 volts.

Answer
Answer. A

34. When a sodium vapor lamp is switched on, initially the color is

(A) Pink
(B) Yellow
(C) Green
(D) Blue.

Answer
Answer. A

35. In a sodium vapor lamp the discharge is first started in the

(A) neon gas
(B) nitrogen gas
(‘C) argon gas
(D) krypton gas.

Answer
Answer. A

36. A auto transformer used with sodium vapor lamp should have

(A) high efficiency
(B) high step-up ratio
(C) high step-down ratio
(D) high leakage reactance.

Answer
Answer. D

37. The capacitor used in auto transformer circuit for sodium vapor lamps, is for

(A) protection against accidental power failure
(B) controlling illumination level of the lamp
(C) for regulating discharge voltage
(D) for improving the power factor of the circuit.

Answer
Answer. D

38. A mercury vapor lamp gives

(A) pink light
(B) yellow light
(C) greenish blue light
(D) white light.

Answer
Answer. C

39. Under the influence of fluorescent lamps sometimes the wheels of rotating machinery appear to be stationary. This is due to the

(A) fluctuations
(B) luminescence effect
(C) stroboscopic effect
(D) low power factor.

Answer
Answer. C

40. Power factor is highest in case of

(A) Mercury arc lamp
(B) Sodium vapor lamps
(C) Tube lights
(D) GLS lamps

Answer
Answer. D

41. Which of the following electric discharge lamp gives highest lumens/watt

(A) Sodium vapor lamp
(B) Neon lamp
(C) Mercury lamp at low pressure
(D) Mercury vapor at high pressure.

Answer
Answer. A

42. The solid angle subtended at the center of a hemisphere of diameter D will be

(A) 4πD
(B) 2πD
(C) 2π
(D) 4π

Answer
Answer. C

43. Which one of the following is a cold cathode lamp?

(A) Sodium lamp
(B) Neon lamp
(C) GSL lamp
(D) Tube light.

Answer
Answer. B

44. In a mercury vapor lamp light red objects appear black due to

(A) high wavelength of red objects
(B) color mixing
(C) absence of red light from lamp radiation
(D) absorption of red light by the lamp radiation.

Answer
Answer. C

45. The flicker effect of fluorescent lamp is more pronounced at

(A) lower voltages
(B) higher voltages
(C) lower frequencies
(D) higher frequencies

Answer
Answer. C

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