For one dynamo…
Electromagnetism is difficult to think about in the abstract, so it helps to demonstrate how invisible fields work.
[Note: there may be more interesting experiments out there, which we could use instead!]
Materials: - 2-3 magnets - a piece of cardboard - a compass (optional)
Place one magnet on top of the table. Move the second magnet around under the table, and watch how the top magnet moves. How strong is this invisible magnetic force? How far away must the bottom magnet be before the top magnet stops moving?
Put your compass down on the table, and watch what happens to the needle when you move the magnet around the compass. A compass has a magnetic needle to measure the overall magnetic field of the earth, but your magnet creates a stronger field because it is much closer. Don’t keep the compass close to the magnet for a long time, because this will ruin the compass needle!
Materials: - an old (preferably broken) motor - tools to take motor apart
Carefully remove the cover of the motor, on the side where the axel sticks out. A flathead screwdriver, or something skinny and strong, will help you take it off without damaging the motor. While your paper dynamo uses magnets inside a wire coil to make an electric field, the motor uses some coils inside a ring of magnets. A motor works the same way, by using a magnetic field to move the electrons inside the wire, but it is designed to maximize the electricity produced.
A motor spins when you send an electrical current through the wire. The opposite is also true: you can create an electrical current by spinning the motor. [NOTE: lead-in to turbine lesson?]
- pictures of field lines with arrows
- note how LED only lights up one way - can add another LED in opposite orientation
- electrons cascade like bumper cars
- where to find copper wire - where to find small magnets, and whether they work