Magnetic Field Lines
Posted June 6, 2008on:
This is pretty basic, but I find it worth doing. I am truly surprised by just how few of my students have ever done any experiments on their own.
This is simply shaking iron filing over a magnet. This can be done in one of two ways.
- You can do this as an activity where the students do this themselves. In this case, give them a couple of strong magnets with a clear North and South on the ends and a piece of poster board to put on top. Then they can shake the filings onto the poster board and then draw the lines in their notebook.
- You can do this as demonstration on the overhead projector. This is a little more challenging. I’ve done this with a regular overhead slide and it works ok. I’d like to try it with a more rigid piece of thin plastic, it’s really a pain holding the slide on the magnets and not having everything fall. The plastic needs to be thin enough that you can fold it up to pour the filings back into the jar.
I like doing this with a bunch of odd shaped magnets so they can see the lines of force and how they interact. They should do the magnets individually first, then in pairs.
Here’s a little tidbit: as you shake the iron filings onto the paper or overhead, gently tap the paper or overhead. The iron will jump to form the field lines. If you tap too hard, they will all move together, so do this very lightly at first.