basic electrical MCQ ( 41-60 )

41. If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes
(a) 0.4 ohm✔
(b) 0.6 ohm
(c) 0.8 ohm
(d) 1.0 ohm

42. Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open
(a) there will be heavy current in the main line
(b) rest of the two bulbs will not light
(c) all three bulbs will light
(d) the other two bulbs will light✔

43. The four bulbs of 40 W each are connected in series swift a battery across them, which of the following statement is true ?
(a) The current through each bulb in same✔
(b) The voltage across each bulb is not same
(c) The power dissipation in each bulb is not same
(d) None of the above

44. Two resistances Rl and Ri are connected in series across the voltage source where Rl>Ri. The largest drop will be across
(a) Rl✔
(b) Ri
(c) either Rl or Ri
(d) none of them

45. What will be energy used by the battery if the battery has to drive 6.28 x 1018 electrons with potential difference of 20 V across the terminal ?
(a) 5 joules
(b) 10 joules✔
(c) 15 joules
(d) 20 joules

46. A closed switch has a resistance of
(a) zero✔
(b) about 50 ohms
(c) about 500 ohms
(d) infinity

47. The hot resistance of the bulb’s filament is higher than its cold resistance because the temperature co-efficient of the filament is
(a) zero
(b) negative
(c) positive✔
(d) about 2 ohms per degree

48. Heat in a conductor is produced on the passage of electric current due to
(a) reactance
(b) capacitance
(c) impedance
(d) resistance✔

49. The insulation on a current carrying conductor is provided
(a) to prevent leakage of current
(b) to prevent shock
(c) both of above factors✔
(d) none of above factors

50. The thickness of insulation provided on the conductor depends on
(a) the magnitude of voltage on the conductor✔
(b) the magnitude of current flowing through it
(c) both (a) and (b)
(d) none of the above

51. Which of the following quantities remain the same in all parts of a series circuit ?
(a) Voltage
(b) Current✔
(c) Power
(d) Resistance

52. A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will
(a) decrease
(b) increase✔
(c) remain same
(d) heater will burn out

53. In an electric kettle water boils in 10 m minutes. It is required to boil the boiler in 15 minutes, using same supply mains
(a) length of heating element should be decreased✔
(b) length of heating element should be increased
(c) length of heating element has no effect on heating if water
(d) none of the above

54. An electric filament bulb can be worked from
(a) D.C. supply only
(b) A.C. supply only
(c) Battery supply only
(d) All above✔

55. Resistance of a tungsten lamp as applied voltage increases
(a) decreases
(b) increases✔
(c) remains same
(d) none of the above

56. Electric current passing through the circuit produces
(a) magnetic effect
(b) luminous effect
(c) thermal effect
(d) chemical effect✔
(e) all above effects

57. Resistance of a material always decreases if
(a) temperature of material is decreased
(6) temperature of material is increased
(c) number of free electrons available become more✔
(d) none of the above is correct

58. If the efficiency of a machine is to be high, what should be low ?
(a) Input power
(b) Losses✔
(c) True component of power
(d) kWh consumed

59. When electric current passes through a metallic conductor, its temperature rises. This is due to
(a) collisions between conduction electrons and atoms✔
(b) the release of conduction electrons from parent atoms
(c) mutual collisions between metal atoms
(d) mutual collisions between conducting electrons

60. Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as
(a) 4 : 25
(b) 25 : 4
(c) 2 : 5✔
(d) 5 : 2