1. Magnetic Fields

2. Make some iron filings dance
Hold 2 bar magnets under your iron filings case with the like poles facing each other, but not touching. Draw what you observe in your notebook. Make sure to label the drawing as “same poles together.”
It should look something like this:

3. Make some iron filings dance
Hold 2 bar magnets under your iron filings case with the opposite poles facing each other, but not touching. Draw what you observe in your notebook. Make sure to label the drawing as “opposite poles together.”
It should look something like this:

4. What is going on?
No, this isn’t a double-ended firecracker!
What you have just observed is EVIDENCE of the invisible magnetic force. Notice how the iron filings sorta make lines, and they point in a direction that seems to come out of the end of the magnet? These are called magnetic field lines. Try it out – move the magnet under the field viewer.
The magnetic field “comes out” of the south pole of the magnet and “goes in” to the north pole of the magnet. (But nothing is really moving)

5. (Watch this video of iron filings moving through a fluid
What is going on?
Notice that these lines are also 3-dimensional? (They not only lay flat but also poke up from the magnet?) That’s because the field extends from the magnet in all directions at once.
(Watch this video of iron filings moving through a fluid
Click on the picture.)

6. Field lines show strength
The lines show the strength of the magnetic field.
Since the field lines are closer together at the poles, that tells us the field is stronger at the poles.
(draw this in your notes)
Try it out – where is the bar magnet the strongest? At the poles or in the middle?

7. Field lines show direction
The magnetic field lines show the direction of the field. The little iron filing pieces each have a north and a south pole, so they line up according to the force they feel on each of their ends. Field lines never cross or intersect with each other. They actually run THROUGH the inside of a magnet to form loops.

8. A video explanation
Click on the picture to launch the video

9. Now, back to your observation drawings to explain
Like poles repel each other’s magnetic field lines
The magnetic force from one magnet is pushing the filings away. But the magnetic force from the other magnet is also pushing the filings away. So the filings get turned sideways.

10. Like poles repel each other’s magnetic forces
The magnetic forces are avoiding each other, so these two objects will not stick together.

11. Now back to your observation drawings to explain
Opposite poles attract each other’s magnetic fields
The magnetic force in one magnet is attracting one end of the filings. The magnetic force in the other magnet is attracting the other end. So the fillings are “pulled straight” and the lines join.

12. Opposite poles attract each other’s magnetic forces
The magnetic forces join,
so these will stick together.

13. This is why magnets stick to iron-containing things – magnetic fields join together.

14. Try this at home and amaze your little sister!
Exit ticket:
1- Click on the picture to launch the video. 2- Recreate this picture and draw a model of the magnetic field lines between the slime and the magnet. (You do not have to label north and south.) This is your ticket out the door.
Try this at home and amaze your little sister!