Electrical Engineering Questions and Answers

40. A house is served by a 220 V line in a circuit protected by a fuse marked 9 A, the maximum number of 60 W lamps in parallel that can be turned on is

(i) 33
(ii) 44
(iii) 22
(iv) 20

41. In the above problem, in how much time the same amount of water will be boiled if the two heaters are put in parallel ?

(i) 25 min
(ii) 2.5 min
(iii) 6 min
(iv) none of above

42. A resistor R₁ dissipated the power P when connected to a certain generator. If a resistor R₂ is put in series with R₁, then power dissipated by R₁

(i) increases
(ii) decreases
(iii) Remains the same
(iv) Any of above depending upon the relative values of R₁ and R₂

43. How many calories of heat will approximately be developed in 210 W electric bulb in 5 minutes ?

(i) 15000
(ii) 1050
(iii) 63000
(iv) 8000

44. A tap supplies water at 22°C. A man takes 1 litre of water per minute at 37°C from geyser. The power of the geyser is

(i) 2100 W
(ii) 1575 W
(iii) 525 W
(iv) 1050 W

45. Fuse wire is a wire of

(i) high resistance and low melting point
(ii) high resistance and high melting point
(iii) low resistance and low melting point
(iv) low resistance and high melting point

46. Two lamps of 100 W and 200 W rated for 220 V are placed in series and a 440 V applied across them. Then

(i) only 100 W lamp will fuse
(ii) only 200 W lamp will fuse
(iii) both the lamps will fuse
(iv) No lamp will fuse

47. Two head lamps of a car are in parallel. They together consume 48 W with the help of a 6 V battery. The resistance of each bulb is

(i) 2/3 Ω
(ii) 3 Ω
(iii) 4 Ω
(iv) 1.5 Ω

48. A coil of wire of resistance 50  is embedded in a block of ice. What is the amount of ice melted in 1s if a potential difference of 210 V is applied across the coil ?

(i) 2.625 g
(ii) 3.25 kg
(iii) 4.12 kg
(iv) none of above

49. Two electric bulbs whose resistances are in the ratio 1 : 2 are connected in parallel to a constant voltage source. The powers dissipated by them are in the ratio

(i) 1 :2
(ii) 1 : 1
(iii) 2 : 1
(iv) 4 : 1

50. A 40 W tube light is in parallel with a room heater on a main line. What happens when light is switched off ?

(i) The heater output remains the same
(ii) The heater output is larger
(iii) The heater output is smaller
(iv) None of the above

51. A battery supplies 150 W and 196 W power to two resistors of 6 Ω and 4 Ω when they are connected separately to it. The internal resistance of the battery is

(i) 0.5 Ω
(ii) 1 Ω
(iii) 1.5 Ω
(iv) 2 Ω.

52. In the circuit of above Figure, the bulb B does not light although ammeter A indicates that current is flowing. Why does the bulb not light ? The switch is in closed position.

(i)The bulb is fused
(ii) There is a break in the circuit between bulb and ammeter
(iii) The resistance of variable resistor is too large
(iv) There is a break in the circuit between bulb and variable resistor

53. Of the two bulbs in a house, one glows brighter than the other. Which of the two has a large resistance ?

(i) the dim bulb
(ii) the bright bulb
(iii) both have same resistance
(iv) brightness does not depend upon resistance

54. A constant voltage is applied across the ends of a conductor. The heat produced is

(i) directly proportional to length
(ii) inversely proportional to length
(iii) directly proportional to square of length
(iv) none of above

55. Two bulbs of equal wattage, one having carbon filament and the other having tungsten filament, are connected in series to the mains, then,

(i) Both bulbs glow equally
(ii) Tungsten filament glows more
(iii) carbon filament glows less
(iv) carbon filament glows more

56. A d.c. supply voltage has an internal resistance of r ohm. A resistive load R is connected across the terminals of the supply. The power developed in R is maximum when the value of R is

(i) √r ohm
(ii) r² ohm
(iii) r ohm
(iv) none of above

57. Two identical heater coils are connected in parallel across the mains. If one of the coil breaks, the other coil

(i) develops lower temperature
(ii) develops same temperature as before
(iii) develops higher temperature
(iv) will also not be heated

58. The power rating of a motor drawing a current of 40 A at 400 V is

(i) 16000 W
(ii) 400 W
(iii) 10 W
(iv) 0.1 W