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224 THE BOY ELECTRICIAN

fact that the lighting system in their town furnished alter-
nating current. Very often in the case of small cities or
towns one power-house furnishes the current for _ several
communities and the energy has to be carried a consider-
able distance. Alternating current is then usually em-

' ployed.

The illustration shows the general method of arranging
such a system. A large dynamo located at the power-house

 

 

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POWER HOUSE GENERATING
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FIG. r76. — Alternating Current System for Light and Power.

generates alternating current. The alternating current
passes into a “ step-up ” transformer which raises the
potential to 2,200 volts (approximately). It is then pos-
sible to use much smaller line wires, and to transmit the
energy with smaller loss than if the current were sent out
at the ordinary dynamo voltage. The current passes over
the wires at this high voltage, but wherever connection is
established with a house or other building, the “ service ”
wires which supply the house are not connected directly to

POLE TRANSFORMER

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