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generator produces electricity that
causes the electron's to change direction. As shown in Figure 1. 15, electron flow is
clockwise for period 1 and anticlockwise for period 2.
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Alternating current is the more
common type of electricity as permanent supply to commercial and industrial buildings and domestic
premises.
Figure 1.15. Alternating current.
Figure 1.16 is a graphical representation of alternating current called a sine
wave. Note the two axes. The vertical axis represents the direction and magnitude of
the current; the horizontal axis represents time.
When the wave form is above the time axis, current is flowing in what is called the positive
(+) direction. When the wave for is below the time axis, the current
is flowing in the opposite, or what is called the negative (-)
direction.
In period 1, current starts at zero magnitude, increases to a maximum magnitude, and
diminishes back to zero.
Figure 1.16. Alternating current sine wave. In period 2 shown
in Figure 1.17, current flow reverses direction and
immediately begins to increase in the negative direction. When current flow
reaches maximum magnitude, it diminishes until it reaches zero again.
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The pattern of alternating current
flowing first in the positive direction (period 1) and then in the negative direction (period 2),
is called one cycle (periods 1 + 2).
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