An electric current flows into the motor through a wire. The wire inside an electric motor is wound into a coil that can turn round, or rotate. This coil of wire is placed between the two poles of a fixed magnet. When an electric current flows through the wire, it creates a magnetic field around the coil, with a north pole at one side and a south pole at the other. If the south pole of the coil is near the south pole of the fixed magnet, the two like poles repel each other and the coil turns round. The coil rotates halfway round the circle, and stops when the south pole of the coil is next to the north pole of the magnet. How can you make the coil go on turning? If you change the direction of the electric current, the south pole of the coil becomes a north pole. The north pole of the coil repels the north pole of the magnet, and so the coil rotates around the second half of the circle.
Steps to be taken
1. Ask an adult to push the knitting needle through the centre of the cork lengthways. Stick two pins into one end of the cork. Make sure they are the same distance from the needle. Leave about one centimetre of each pin sticking out of the cork. 2. Wind the wire lengthwise about 30 times around the cork. Always wind it in the same direction. Use sticky tape to hold the wire in place. Remove two centimetres of the plastic covering from the wire ends. 3. Wrap one of the bare wires around one of the pins. Wrap the other bare wire around the other pin. 4. Hammer two nails into each end of the wood base, so they form an X shape. Place the cork so that the needle sits on top of the nails. Make sure that he bottom of the cork does not touch the wood base. 5. Pull out one end of a paperclip and bend it upwards. Fasten the paperclip to the board with a drawing pin so the bent end is in contact with the pin on the cork. When the cork rotates, the pins on the cork should just touch the bent clip. Do the same thing with the second paperclip, placing it on the other side of the needle. 6. Use the short wires to connect the battery to the paperclips. Place one magnet at the side of the cork with the north pole closest to the cork. Place the second magnet on the other side with the south pole closest to the cork. Spin the cork and your motor will start. If the motor stops, check each part until you find out why it isn't working.
Two pins, about 3 cm long
5 metres of plastic-coated wire
A piece of wood, about 15 cm x 10 cm x 1 cm
Two lengths of plastic-coated wire, 25 cm long, with bare ends
Four nails, about 5 cm long
Two drawing pins
A thin, steel knitting needle, about 10 cm long
A large cork A 4.5 volt battery Two strong bar-magnets