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Graphs are one way of
showing the relationship
between two variables
(things that can change
in value).
The graph above shows
how the brightness of
the sun is related to
the time of day.
From the start at the
bottom left hand corner
until just before 6 am
brightness is zero. (It
is dark).
Brightness increases as
time passes being at
maximum about 1 pm when
the sun is highest in
the sky.
Brightness then falls
becoming dark at about 9
pm when the sun sets.
Now look at the
following graph.
This relates a dry
battery voltage to time.
It falls slowly over the
weeks.
This next graph shows a
voltage which slowly
rises from zero to a
maximum value and then
falls suddenly to zero
again.
This next graph shows
the same thing happening
but continues repeating.
This is called a
WAVEFORM.
The next waveform is
called a square waveform
because of its shape.
It is at zero for a time
and then shoots rapidly
to a maximum value and
stays there for a time
before falling to zero
again.
It then repeats itself
continuously.
An OSCILLOSCOPE is used
to display and measure
waveforms.
A common waveform is the
SINEWAVE which can
alternate between
positive and negative
voltages.
Note that the horizontal
line in all these graphs
is called the X axis and
the vertical line is the
Y axis.
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