PASCO SE-8658A PERMANENT MAGNET MOTOR - Manual (Page 14)

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Permanent Magnet Motor 012-07210A
7. Turn the armature over 180° and imagine that the brush attached to the + lead is contacting the other
split ring of the commutator. Note the path of the wire from where it is attached to the split ring to
where it enters and exits from the coil on the right side of the armature. Imagine a current running
through the wire and use the right-hand rule to determine the direction the magnetic field would
flow. Is the north pole on the same end of the coil as it was in step 5?
8. Follow the wire over to the left coil. Use the right-hand rule to find the direction of the north pole.
a) In this situation, is the direction of the north pole the same for the right and left coils?
b) True or False? When the electric current is on, the two coils become electromagnets with
magnetic fields oriented in the same direction, which turns the armature into a single
electromagnet with its force oriented towards that same direction.
c) True or False? In the DC motor, you cannot determine the direction of the magnetic field of
the armature by determining the direction of the north pole of either of the two coils.
d) What happens to the location of the armature’s north pole as the brush attached to the + lead
touches the different sides of the split ring commutator?
e) Explain why the current in the armature is alternating, despite the fact that the motor is supplied
with direct current. (Hint: think about your answer to 8d.)
9. Gently replace the armature onto the shaft with the split ring commutator pointing down. Carefully
rotate the armature back and forth to separate the brushes and allow the commutator to slip down
between them. If necessary, insert a pencil or similar object between the brushes to separate them.
Use only the most delicate force to avoid bending the brushes and necessitating adjustment or
repairs.