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
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
Which of the following quantities remain the same in all parts of a series circuit ____________?
A. Voltage
B. Current
C. Power
D. Resistance
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
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
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
A closed switch has a resistance of_____________?
A. zero
B. about 50 ohms
C. about 500 ohms
D. infinity
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
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
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