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
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.