Electrical Energy and Work
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| Electricity is
produced by converting other forms of energy like heat or light. The
supply company then distributes this energy to consumers over high
voltage overhead wires. When close to the consumer the energy is changed
to the low voltage supply available at a standard electrical socket.
A unit of energy is known a joule. Energy is the ability to
do work. It can be said that when energy is transformed from
one form to another, work is done. |
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Power
Power is the rate that energy is used or work is
done. The unit of power is the watt with a symbol of the
letter W. The watt is named after James Watt the English inventor
who was responsible for the term 'horsepower'. One horsepower is
equal to 746 watts.
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Efficiency
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| All systems have losses which is power used in excess
to the requirements of the load. These losses can be mechanical and/or
electrical. Efficiency is expressed as a percentage of the ratio of
power output to power input. The symbol is n (pronounced 'eta') expressed
in a number followed by the percent symbol; e.g., efficiency = 89% |
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Definitions
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Work
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is done when energy is converted from
one form to another, e.g. from sunlight to voltage
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Power
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is the rate of doing work
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Energy
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is the ability to do work
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Torque
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| Torque is the term used for
for the effect of a force producing rotation about a a point. Torque
can only be present when there is rotation. |
| The ability of an electric motor to turn
a shaft is measured in torque. |
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