Quick Lab
Observing Magnetic Field Lines
Materials
small container of iron filings, 2 bar magnets, paper, 2 textbooks, masking tape
Procedure
Place two textbooks side by side, about 7 cm apart.
Place the magnets between the books, with north poles facing, about 2 cm apart. Tape the magnets in place.
Place the paper over the magnets to form a bridge.
Sprinkle iron filings on the paper until you can see the magnetic field lines. Sketch your observations.
Carefully return the filings to their container.
Repeat Steps 2 through 5 with opposite poles facing.
Analyze and Conclude
Inferring Where was the magnetic field the strongest? The weakest?
Analyzing Data How did the fields of like poles facing differ from those of unlike poles facing?
Predicting What result would you expect if you used sawdust instead of iron filings?
Magnetic Field Around Earth
Earth is like a giant magnet surrounded by a magnetic field. The area surrounding Earth that is influenced by this field is the magnetosphere (mag NET oh sfeer).
A compass points north because it aligns with Earth's magnetic field. However, as Figure 4 shows, Earth's magnetic poles are not at the geographic poles. The geographic North Pole is at 90°N latitude, but the magnetic North Pole is at about 84°N latitude. Because of this, a compass may point east or west of north. The angle between the direction to true north and to magnetic north is called magnetic declination. Magnetic declination varies with your location on Earth.
Why does a compass point toward north?
Magnetic Materials
Within an atom, electrons move around the nucleus. This movement, along with a property of electrons called “spin,” causes electrons to act like tiny magnets. In many materials, each electron is paired with another having an opposite spin. Magnetic effects mostly cancel each other. As a result, these materials have extremely weak magnetic fields.
Many other materials have one or more unpaired electrons. The unpaired electrons produce magnetic fields. But the fields usually don't combine because the arrangement of the atoms isn't quite right. These materials have weak magnetic fields. In a few materials, such as iron, nickel, and cobalt, the unpaired electrons make a strong magnetic field. Then the fields combine to form magnetic domains. A magnetic domain is a region that has a very large number of atoms with aligned magnetic fields. A ferromagnetic material (fehr oh mag NET ik), such as iron, can be magnetized because it contains magnetic domains. 
When a material is magnetized, most of its magnetic domains are aligned.
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