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प्रश्न
An electric heater is rated 220 V, 550 W. Electrical energy is also measured in kWh. What do you understand by a kilo-watt-hour?
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उत्तर
The energy consumed in a resistor when the potential difference is 1V and 1A current flows for 1000 hrs.
संबंधित प्रश्न
An electric bulb is connected to a 220 V power supply line. If the bulb draws a current of 0.5 A, calculate the power of the bulb.
An electrical appliance having a resistance of 200Ω is operated at 200 V. Calculate the energy consumed by the appliance in 5 minutes (i) in joules (ii) in kWh.
What is wrong with the circuit diagram (Fig. 34)? Carefully check the symbols and assign proper positive and negative signs to them.

Why is the electric power from the generating station transmitted at high voltage?
State the reason why, in a three-pin plug, the earth pin is longer and thicker than the other two.
At what voltage is the electric power generated at the generating station? Explain the transmission of this power to your house.
Three 250 W heaters are connected in parallel to a 100 V supply, Calculate the resistance of each heater.
An Electric bulb is marked 100 W, 230 V. What find the energy consumed by the bulb in one hour.
The following table gives the electrical appliances used, their power and the average time for which they are used each day in a home. Estimate the monthly electricity bill if the rate is 60 paise per unit.
| Sr.no. | Name | Nos. | Power rating | Time/day |
| 1 | Bulb | 4 | 100 W | 7.5 hr |
| 2 | Fans | 2 | 50 W | 10 hr |
| 3 | T.V. | 1 | 100 W | 2 hr |
| 4 | Iron | 1 | 500 W | 1 hr |
| 5 | Electric stove | 1 | 750 W | 2 hr |
