Video: Watch this demo
Description: This demo shows that a moving magnetic field induces a current in a coil of wire, which can be displayed on an overhead projector.
It also shows that the direction of the moving magnetic field determines the flow of current.
- Bar magnet
- 250 or 1000 turn coil
- Two long banana plug cables
- Magnetize the bar magnets prior to use with the electric magnetizer.
- Connect the galvanometer to the wire coil.
- Test to make sure the galvanometer has the appropriate sensitivity. If too sensitive, use less turns. If not sensitive enough, use more turns. (remember you can use the half turn tap on some coils)
- Place the galvanometer on the overhead projector and focus it.
- Turn on the projector.
- You may start by having the coil stationary and moving the magnet in and out of the coil.
- Note that moving toward the magnet makes the needle move one way, while moving away from the magnet moves it in the opposite direction. Explain that this is analogous to AC current.
- You may also show that the only thing that matters is the relative movement between the two.
- With the magnet fixed, move the coil back and forth
Note: The individual coils are more effective.
If using one with too many turns though, you may peg the galvanometer needle with the slightest movements.