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
Ans: a
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
Ans: d
55. Resistance of a tungsten lamp as applied voltage increases
(a) decreases
(b) increases
(c) remains same
(d) none of the above
Ans: b
56. Electric current passing through the circuit produces
(a) magnetic effect
(b) luminous effect
(c) thermal effect
(d) chemical effect
(e) all above effects
Ans: c
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
Ans: c