Children

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Build an electric motor

YOU NEED:

  • Two small AA batteries
  • Four wire supports bent
  • Five metres of insulated copper wire
  • Baked insulation, not plastic
  • Two small magnets
  • Block of wood
  • Sticky putty
  • Crocodile connector clips

WHAT TO DO:

Turn the copper wire in a coil about 2.5 cm in diameter.
Position the tips of the wire in opposite directions, again about 2.5 cm of tip on both sides.
Now carefully scrape off the baked insulation on only one side of the wire at both ends. This is very important.
Do not scrape off all the insulation. Only half of the actual diameter ff the wire must be cleaned. Make sure the cleaned halves are on the same side of the two opposing tips.
These will be the contact points for your electric motor.

Use a pair of pliers to bend small loops in the 4 cm wire supports as shown. Drill four small holes in a piece of wood to position the wire supports. Attach the two magnets on opposite sides with stickey glue to the wire supports.

Position the copper coil in the other two supports so that it can rotate freely
between the two magnets.
Attach the batteries to the wire supports that cradle the coil with crocodile clips.

Start the motor by spinning it on its axis by hand.
If everything is connected up the coil will keep spinning.
You might have to experiment a bit with the best position of the magnets and it can take quite a bit of effort to get it going.
But once it spins it really goes!

The Science

This is a brushless DC motor.

The electric current flowing in the copper coil sets up an electro magnetic field opposing the magnetic field of the two fixed magnets.

At first the coil will position itself in a flat plane between the fixed magnets. This is the result of the two magnetic fields apposing each other.

Once you spin it, it will keep trying to turn out of the fixed field but its own momentum will cause it to over shoot and the two magnetic fields to interact again and again, and it just keeps on turning.

Have fun and read up on the direction of the magnetic field caused by electric current flowing in a coiled conductor.