PASCO SE-8658A PERMANENT MAGNET MOTOR - Manual (Page 12)

8
Permanent Magnet Motor 012-07210A
Procedure—Part A
1. Rotate the armature and observe how the
segments of the split ring commutator contact
the brushes as the armature turns.
2. Remove the armature from the shaft by grasping it between your thumb and forefinger and rotating
it back and forth while lifting gently. If necessary, insert a pencil between the brushes to gently
separate them to remove the armature.
3. Examine the armature closely and imagine current entering one of the split rings from a brush.
Trace the path of the current through the wire to the coil, through the coil, through the wire to the
coil on the opposite side of the armature, through that coil, and through the wire to the other split
ring and into the second brush. By carefully examining the part of
the coils where the wire emerges from the coil, you can determine
the direction in which the wire is wound on the coil (Figure 1.3).
4. Holding the armature in one hand, imagine that the brush from the
+ lead is touching one of the split rings of the commutator.
Follow the wire from the split ring to the right coil of the armature
and note the direction the wire is wound in the coil. Note where
the wire enters the coil and where it exits.
5. Use the right-hand rule to determine the direction the magnetic
field will flow when you turn on the power: Grasp the coil with
your fingers wrapped around the coil in the direction of the current
(Figure 4). (Current direction is described by convention as being
from the positive to the negative lead. Note that this is opposite of
the direction of electron movement. — See note on page 10. Your
thumb will point in the direction of the field — that is, toward the
north pole of the coil.) Put a small piece of tape on the end of the
armature that will be its north pole when you turn on the power.
6. Follow the wire over to the left coil. Use the right-hand rule to
find the direction of the north pole.
Record your observations on Figure 1.4.
a) In this situation, is the direction of the north pole the same for the right and left coils?
b) Both coils surround a single iron core on the armature, and each coil is capable of temporarily
magnetizing the core when electric current is running through it. Do the actions of the two
coils add to create a greater effect or cancel to create a reduced effect? (Consider your answer
to 6a above.)
• 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.)
➤ Do not turn the power on.
Figure 1.3
Direction of the Wire Winding on
the Coil
Figure 1.2.
Experimental Setup
6 AMP
MAX RESET
ON
OFF
PASCO
scientific
METER
PUSH FOR
CURRENT
DC CURENT
ADJUST
DC VOL
TAGE ADJUST
2
4
6
8 12 14
16
18
20
22 24
10
AC VOL
TAGE
ADJUST 2 - 24 VOL
TS AC OUTPUT
0 - 24 VOL
TS DC OUTPUT
8 AMP
MAX
MODEL
SF-9584 LOW VOL
TAGE
AC/DC POWER SUPPL
Y
wire connected to + terminal of power supply