PASCO SE-8658A PERMANENT MAGNET MOTOR - Manual (Page 20)

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Permanent Magnet Motor 012-07210A
b) To oppose the motion during the second 90 degrees of rotation, which pole (N or S) would the
taped end of the armature need to be?
9. In order to cause the armature to act as you stated in step 8 above, which direction would the
induced current need to move?
a) Must electronic current enter or leave the coil from the upper brush, in order to make the
armature act as you described in 8 (a) above?
b) Must electronic current enter or leave the coil from the upper brush, in order to make the
armature act as you described in 8 (b) above?
10.Use a voltmeter set on a DC millivolt range to test your predictions. When electronic current
enters the positive terminal of a meter, the value will be positive. If electronic current enters the
negative terminal, the needle will swing left (unless prevented by a peg in the meter) and, in a
digital meter a negative result will be displayed.
a) Test your predictions for 8 (a) and (b) above: After connecting the meter to the brushes, repeat
the two 90-degree rotations, taking about one-half second for each. Comment on your
findings.
11.a)
Using the same reasoning as before, predict the direction(s) of the current during the next 180-
degree rotation, following the one you just made.
b) Test your predictions with the meter and comment.
c) What changes if the armature is rotated in the opposite direction?
12.As the armature rotated, the current changed both in magnitude and direction. This is called
alternating current. If this generator were rotated at 3600 revolutions per minute, what would be
the frequency of the alternating current?