Red Nose Day

electricity and magnetism

electricity and magnetism

Hans Oersted, the nineteenth century Danish scientist, first proved the relationship between electricity and magnetism when he noticed that a magnet held near to a compass caused it to turn. When this experiment was repeated, replacing the magnet with a current of electricity, he observed the same effect. This was the beginning of electromagnetism. After Oersted's experiments, it was soon realised that magnets could be made by passing an electric current through coils of wire. The magnetic field (the region around the wire where the force of magnetism is felt) could be switched on and off with the electricity. When a doorbell is pressed, an electromagnet attracts, a clapper to strike the bell. Use electromagnetism to hold the clown's nose in place.

Red Nose Day

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1. Take a piece of thick board and push a nail through the centre. Now wind a piece of wire around the nail at least 20 times, leaving two ends of the same length.

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2. Cut two triangular pieces of polystyrene to support the board in a sloping position.

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3. Attach the triangles, as shown, and pierce a small hole in the side of one of them for a paperclip to fit through.

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4. On a second sheet of polystyrene draw a clown's face to fit on top of the shape you have made. Do not draw a nose on the face. Colour the face, then cut out your clown.

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5. Fix a drawing pin to the side of a ping-pong ball, coloured red. This will be your clown's nose. It will not fit in place yet.

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6. Position the batteries inside the shape as shown. Make sure unlike terminals are touching. Now connect a wire from the nail to one end of the batteries using plasticine. Connect the other to the paperclip.

Bright Ideas

• H Reproduce Oersted's experiment. Magnetize a needle and rest it on a piece of folded cardboard that is balancing on a stick. Place it in ajar - this will act as a compass. Now set up a simple circuit, allowing the wire to run above the magnetized needle. Observe the effect on the needle when the current flows. Wind more lengths of wire round your compass. What difference does this make? Find out which appliances contain electromagnets - a telephone contains one.
• Can you design a burglar alarm that works because of the effect of an electromagnet?

Why It Works

temporary magnet

When the current is switched on, the nail becomes a temporary magnet. The clown's nose stays in place, held in the magnetic field created by the electricity. When the electric current is turned off, the nose falls off. The nail loses its magnetic properties.

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7. Push the paper clip through the hole until it touches the adjacent battery terminal. Leave half of the paper clip protruding through the hole. Position the red nose on the clown's face.

Red Nose Day

8. While the paperclip is pushed in wards, the nose will stick to the clown’s face. Now pull the paperclip outwards. The clown’s nose will roll of this face.