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It Can't Work


How can you make a simple electric motor?


Base: 10 cm x 10 cm corrugated cardboard
Brushes: 2 paper fasteners, two 8 cm bare
wire, small nail to form loops
One 20 cm enameled wire for armature,
sandpaper, one small magnet, 1.5 volt dry cell


1. Space two brass fasteners about 5 cm apart and push them through the
cardboard about 1 cm from the edge. Bend the fasteners on the bottom of the

2. Wrap the middle of an 8 cm bare copper wire around each fastener head. Make a brush loop about 4 cm up from each fastener by wrapping the bare wire several times around a small nail.

3. Sandpaper about 3 to 4 cm coating off each end of a 20 cm piece of enameled wire. Be sure the ends are clean and shiny. Wrap about 3 to 5 turns of the enameled wire around a finger to make a coil as shown. Put piece of cellophane tape around the coil to keep it together. Bend and form the armature coil so the shaft ends are straight as shown.

4. Put the coil shaft ends through the brush loops. Put a magnet under the coil. Adjust the brush loop height and coil to make the armature level. Be sure that the armature will spin evenly and is not lopsided.

5. Attach a dry cell to the uncoi led brush ends. Spin the armature to start the motor. You may have to make other adjustments to the magnet, supports, and/or armature to get your motor running smoothly. Keep trying!

Summing Up

1. Try making your motor run in reverse.

2. Try making various armatures for your motor. Increase or decrease the number of turns in the armature. What effect does this have?

3. How do you think this motor operates?

Teaching Strategies:

The enameled wire may be the most difficult materials for you to find. This wire should be quite thin. Wire from the windings of an old motor or generator would be suitable. The teacher should try this activity before the students do so. Encourage the students to be patient while trying to get the motor to run. Successful students can help others in the class.
Students may try to experiment with oval or flatter shaped armatures.

Summing Up:

The motor operates because as it rotates it also vibrates. This vibration causes the ends of the armature periodically to break contact with the brush loop. Thus, the magnetic field around the armature windings is constantly changing and interacting with the permanent magnet.