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NOTES ON ELECTRICAL TERMS.
NOTES ON ELECTRICAL TERMS.
The units used in electrical calculations are different from
the well-known units used in mechanics. The name of each
unit in electricity is derived from the name of some great scien-
tist who has assisted in the world’s progress. When we become
familiar with their meaning and value, these units are not more
difficult to understand than the common well-known terms, feet,
inches, pounds, gallons, etc
Volt.
Volt is the practical unit of electromotive force, and is such
an electromotive force as will drive one ampere of current
through a resistance of one ohm. The name volt is after an
Italian electrician, Alessandro Volta (1745-1827).
In practice, the electromotive force in volts is measured by
an instrument called a Voltmeter. In calculation we obtain the
volts by multiplying the ohms by the amperes.
As example, we will say that each cell in a storage battery
has an electromotive force of from 2 to 2j£ volts. A common
so-called dry cell will give an electromotive force of about 1 to
V/z volt.
Common 16-candle power incandescent lamps are usually
run on a 110 volt circuit, that is to say, the filament in the
lamp has such resistance that it requires an electromotive
force of 110 volts to drive current enough through the lamp to
give good light.
Electric street cars are usually run on about 500 volt cir-
cuits, that is to say, the windings of the motors are of such pro-
portion that it takes an electromotive force of 500 volts to drive
sufficient current through the motor so it will drive the car at its
proper speed.
Ampere.
Ampere is the practical unit of current strength and is that
current which would circulate in a circuit having one ohm resist-
ance when the electromotive force is one volt. The name
ampere is after a French electrician, Andre* Marie Ampere
(1775-1836).
In practice, the current strength in amperes is measured by
an instrument called an Amperemeter. In calculation we ob-
tain the amperes by dividing the volts by the ohms.
As examples, we may say a common 16-candle power in-
candescent lamp on a 110 volt circuit is using about one-half of
one ampere. A 32-candle power incandescent lamp is using
about one ampere. A motor running on a 110 volt circuit will
take about 7 amperes to produce 1 horse power.
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