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# Permanent: How Can You Model a Permanent Magnet?

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Source:
Author: Janice VanCleave

### Problem

How can you model a permanent magnet?

### Materials

• iron (steel) nail
• paper clip
• bar magnet

### Procedure

1. Touch the nail to the paper clip to make sure they are not attracted to each other.
2. Lay the nail on a wooden table.
3. Hold the south-pole end of the magnet on top of the center of the nail.
4. With the south-pole end of the magnet, stroke the nail toward its point 30 times. Be sure to lift the magnet away from the nail when returning to the starting point for each stroke.
5. Touch the pointed end of the nail to the paper clip.

### Results

The paper clip clings to the iron nail.

### Why?

Iron and other magnetic materials act as if they have millions of tiny magnets inside them that point in different directions. The correct name for a tiny magnet within a magnetic material is a domain. The bar magnet is a permanent magnet (a magnet that does not easily lose its magnetism). Stroking the nail with the bar magnet causes the domains inside the nail to line up. A permanent magnet can be made with this method, but most permanent magnets are made of mixtures of iron, nickel, cobalt, and other substances such as aluminum. The strength of any magnet depends on the number of domains that are lined up and facing the same way. A completely magnetized material has all of its domains facing in the same direction.

### Let's Explore

1. Would stroking the nail with the north pole of the magnet affect the results? Repeat the experiment using the north pole of the magnet.
2. Would stroking the nail more times increase its magnetic strength? Repeat the original experiment twice, increasing the number of strokes. First stroke the nail 50 times on each end, and then try 75 strokes.
3. Would stroking the nail back and forth make a difference? Repeat the original experiment, but instead of lifting the magnet back to the starting point, drag the magnet back across the nail.

### Show Time!

How does rubbing a magnetic material with a magnet affect the polarity of the material? Repeat the original experiment to produce a magnetized nail. TIe a piece of thread to the center of the nail. Tape the free end of the thread to a pencil. Lay the pencil across the mouth of a glass jar so that the nail hangs freely inside the jar. Use a compass to determine which end of the nail is pointing north. From your results, write out a procedure so that the pointed end of one nail can be magnetized to become a north pole and the pointed end of a second nail can be magnetized to become a south pole.

### Check It Out!

1. Iron, nickel, and cobalt are the only three metals that are attracted to a magnet. A mixture of any two or more metals is called an alloy. Mixtures combining one or more of the three magnetic metals with other metals can produce a magnetic alloy if the percentage of magnetic material is high enough. Read about alloys of magnetic materials. Some things to discover in your research are:
• why a magnet is attracted to a Canadian nickel but not to a United States nickel.
• why the alloy called alnico is more magnetic than a natural iron magnet.
• what metals make up alnico and other magnetic alloys such as stainless steel and nichrome.
2. Find out how commercial magnets are made. A strong permanent magnet can be made by winding a coil of wire around a core of magnetic material, such as iron. An electric current is passed through the coil, which produces a magnetic field inside the coil. This magnetic field magnetizes the iron core by induction. (See Experiment 15 for an explanation of induction.) Find out more about using electricity to produce magnets. Is the strength of the magnet increased by an increase in current? Would the number of coils around the core affect the strength of the magnet produced?