The Energy of Electric Currents
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-291
2025-12-10
10
-The energy required to send a current varies directly as the current and also as the potential difference. When a difference of potential at the terminals of a circuit is 1 volt and this sends a current of 1 ampere through the circuit is 1 watt, or 1/746 horse power In any circuit the number of watts equals the number of volts the number of amperes; i.e., W = VA. The number of watts required to burn a certain tungsten lamp in which a current of 0.363 ampere is used, on a 110-volt circuit, will be 110 × 0.363 =40 watts. The practical unit of power is the kilowatt, equal to 1000 watts.
The kilowatt equals 4/3 horse power and one horse power equals 4/3 kilowatt. The practical unit of work is the kilowatt hour, or the work done in one hour at the rate of 1 kilowatt - namely 3,600,000 joules.
The work done in burning incandescent lamps is measured in watt hours; the charging of a storage battery, in kilowatt hours. A battery of 55 cells, charged from a circuit giving a potential drop of 110 volts across the battery terminals and sending a current of 25 amperes through the cells for one hour, would have 2.75 kilowatt hours of work done on it.
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