An electric bulb is rated 250W, 230V. The time in which the bulb will consume 1.0kWh energy when connected to 230V mains will be :
A
4h
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B
2h
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C
6h
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D
1h
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Solution
The correct option is B4h The electric power in watts associated with a complete electric circuit or a circuit component represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, e.g., heat, mechanical energy, or energy stored in electric fields or magnetic fields. The power is given by the product of applied voltage and the electric current. That is, P=VI.
The power dissipated is given as 250W and the energy dissipated is 1kWh230V.
To calculate kWh, we take the wattage of the device, multiply that by the number of hours it's used, and divide by 1,000. That is, in this case, 250W×timetaken1000=1kWh. The above relation is rearranged as 1kWh×1000=250W×timetakent,thatis,t=1×1000250=4hours Hence, the time taken for the energy of 1 kWh to be consumed is 4 hours.