©
COPYRIGHT 1999 THE ESAB GROUP, INC. LESSON
I, PART B 1.8.3.2
For example, if an appliance is designed
for the common household primary voltage
of 115 and the wattage stamped on the appliance faceplate is 5, then the
amperage drawn by the appliance when
in operation is determined as shown: 5
÷ 115 = .04 amperes 1.8.3.3
Kilowatt is another term common in
electrical usage. The preface "kilo" is a
metric designation that means 1,000
units of something; therefore, one kilowatt is 1,000 watts
of power. 1.8.4
Power
Generation -
Electrical energy is supplied either as direct current (DC) or
alternating current (AC). With
direct current, the electron movement within the conductor is
in one direction only. With alternating
current, the electron flow reverses periodically. Al-
though some types of electrical generators
will produce current directly (such as batteries, dry
cells, or DC generators), most direct current is developed from alternating current.
1.8.4.1 Through
experimentation, it was discovered that when a wire is moved through a
magnetic field, an electrical current
is induced into the wire, and the current is at its maximum
when the motion of the conductor is at right angles
to the magnetic lines of force. The sketch in
Figure 9 will help to illustrate this principle. 1.8.4.2
If the conductor is moved upwards in
the magnetic field between the N and
S poles, the galvanometer
needle will deflect plus (+). Likewise,
if the conductor is moved downwards the
needle will deflect minus (-). With this principle
of converting mechanical energy into electrical
energy understood, we can apply it to the
workings of an AC generator. 1.8.4.3
Figure 10 is a simplified sketch of
an AC generator.
Starting at 0° rotation, the coil wire is moving
parallel to the magnetic lines of force
and cutting none of them. Therefore, no current is
being induced into the winding.
1.8.4.4 From
0° to 90° rotation, the coil wire cuts an increasing number of magnetic
lines of force
and reaches the maximum number at 90° rotation. The current increases
to the maximum
because the wire is now at right angles to the lines of force.
FIGURE 9 GALVANOMETER
ELECTRO-MAGNETIC
INDUCTION
