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# Arrangements of Permanent Magnets: What is the Shape of a Magnetic Field?

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Source:
Author: Jerry Silver

### The Idea

You cannot see a magnetic field. But you can define the shape of the field by measuring its effects. In this project, you trace the shape of the magnetic field created by various arrangements of permanent magnets.

### What You Need

• 2 bar magnets
• U-magnet
• several sheets of paper
• iron filings

### Method

1. Lay the bar magnet on the table.
2. Place the sheet of paper over the magnet.
3. Trace the outline of the magnet, showing the north and south poles.
4. Evenly sprinkle iron filings over the paper. Distribute the filings so the shape of the pattern on all sides of the magnet is delineated by the iron filings.
5. Repeat with the following cases.
6. The iron filings can be easily poured back into the container. If they come into direct contact with the magnet, it is much harder to clean up.
• Two north poles facing each other
• A north and a south pole facing each other
• A horseshoe magnet

### Expected Results

The electric field surrounding a bar magnet follows lines that go from the north pole to the south pole, as shown in Figure 111-1.

With a north pole directly opposite a south pole, the lines of force are directed from the north pole to the south pole, as shown in Figure 111-2. With two north poles facing each other, the electric field is directed away from each of the poles. Lines of force can be seen directed perpendicular to each of the two magnets, as shown in Figure 111-3.

### Why It Works

The magnetic field causes ferromagnetic materials, such as iron filings, to align with the field lines.

### Other Things to Try

A higher tech approach would be to use a magnetic field sensor to map out the shape of these magnetic fields.

### The Point

Magnetic fields show the force a magnet would exert on the north pole of another magnet. Magnetic fields point from north to south. Magnetic fields point away from north poles (opposites repel) and toward south poles (likes attract).