When all the instantaneous values of an alternating voltage or
current (A.C.) are plotted on a time line, marked off in degrees
of rotation, the result is a sine wave.
You will now be shown how to draw a graph of the sine function, commonly called a
sine curve or sine wave.
When a resultant vector is rotated from 0 through 360 (four quadrant), the side
opposite (y vector) increases from zero to maximum positive magnitude in the first
quadrant; decreases from maximum positive magnitude to zero in the second quadrant;
increases to maximum negative magnitude in the third quadrant; and, finally, decreases
back to zero magnitude in the fourth quadrant.
This variation of the y vector can be seen by plotting the magnitudes of the y vector
above or below the horizontal reference line (the X axis) for each degree of rotation of
the resultant vector.
Keep in mind, as you progress through this objective, that the altitude, or magnitude of
the side opposite (the y vector) represents e .... the INSTANTANEOUS value of a
constantly changing voltage or current.
(CONTINUED ON NEXT PAGE)