PASCO SE-8657 MOTOR ACCESSORY - Manual (Page 26)

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Motor Accessory 012-06247A
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Procedure—Part B
➀
Adjust the gap of the Variable Gap Magnet so there is approximately 1 mm of clearance
between the pole pieces and the armature when it is rotated by hand.
Connect the motor to the power source by one of these methods (See Figure 2):
- Insert banana plugs into the openings in the ends of the plastic brush holder; or
- Grip the brass posts of the brush holder with large alligator clips; or
- Attach small alligator clips to the ends of the brass strips that serve as brushes.
Adjust the power source to deliver 6 volts of DC current limited to 1.0 amp. (Have your
teacher show you how if you don’t know.)
➁ Hold the armature in a position like that shown in Figure 2. Hold the ceramic magnet near
the ends of the armature in order to establish which end is a north pole and which is a south
pole. The painted face of the magnet is its North Pole (north-seeking pole). [You can verify
this by hanging the magnet from a thread and observing that the painted face points toward
the North (toward the earth’s north magnetic pole, located in northern Canada).] If both
poles of the ceramic magnet attract the armature, the pole with the stronger attraction will be
the opposite pole. Verify that the result of the tests agree with your results from step 3.
Determine the polarity of the Variable Gap Magnet in the same way.
➂
Now set the power source to furnish to the brushes with alternating current with a sinusoidal
Figure 2. Experimental Set up
T T
H I ý
G N
L O
M I
R A N
A D J U
M A
O U T P
A M
P L I T
P I-
9 5 8 7 C
D IG
I TA L F U N C T IO
N
W AV E F
I N P
G N
E X T E R
F R E Q U E N C Y - H ER TZ
= D C
digital function
generator-
amplifier
waveform at a frequency of about 30 Hz and voltage of about 6 volts. Rotate the armature
by hand slowly through one complete revolution.
a) Describe the sensation you feel.
b) Explain why this happens.
➃
Repeat this with 30 Hz and 4 volts.