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# Form 3 Physics: Heating Effect of an Electric Current Questions and Answers

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Lessons (**15**)

- 1.
When a current of 2.0A flows in a resistor for 10 minutes, 15,000 joules of electrical energy is dissipated. Determine the voltage across the resistor.

2m 16s - 2.
An electric bulb rated 40W is operating on 240V mains. Determine the resistance of its filament.

1m 10s - 3.
An electric heater rated 3000w is to be connected to a 240V mains supply, through a fuse 10A fuse. Determine whether the fuse is suitable or not.

1m 26s - 4.
An electric kettle is rated at 1.8kW, 240V.Determine the rating of the fuse that may be used in the kettle.

1m 40s - 5.
A hair drier is rated 2500w, 240v.Determine its resistance.

1m 37s - 6.
State how heating is achieved in a resistance wire.

1m 14s - 7.
A 60w bulb is used continuously for 36hours. Determine the energy consumed. Giving your answer in kWh

1m 5s - 8.
An electric bulb with a filament of resistance 480 ohms is connected to a 240v mains supply. Determine the energy dissipated in 2 minutes.

1m 46s - 9.
An electric bulb is rated 75w, 240v.Determine the resistance of the bulb.

1m 20s - 10.
A 4 ohms resistor is connected in series to a battery of e.m.f. 6v and negligible resistance. Determine the power dissipated by the resistor.

0m 54s - 11.
A Current I flowing through a wire of resistance R was increased seven times. Determine the factor by which the power was increased.

2m 7s - 12.
An electric heater is connected to the mains supply. A fault in the mains reduces the supply potential slightly. Explain the effect on the rate of heating of the heater.

1m 16s - 13.
A heating coil is rated 100w, 240v.What will be the power dissipated by the coil if it is connected to a 220v supply.

1m 52s - 14.
Two points A and B have the potential difference v volts. Q coulombs of charge flows between A and B for t seconds. Determine:
i).the electrical energy transformed between the two points in terms of Q.
ii).the power transformed in terms of Q and t.
iii).show that the power transformed is given by P=IV.

2m 50s - 15.
The lighting in a house has 20 lamps each rated 60w, 240v.Determine whether a fuse rated 4A can be used in the circuit when all the lamps are put on.

0m 0s