Talk It Over

Magnets pull iron and steel objects toward them. Does it matter how far away from the object the magnet is? How can we measure the effect of distance on a magnet's strength?

Get

• A compass with an easily read number scale (0–90 degrees between major compass points)*
• Sheet of graph paper (ruled in ¼-inch squares)
• Tape
• 1 or more small bar magnets*

Go

1. Place the compass so that the needle points toward your right. The needle should point exactly at one of the 0 (zero) marks, like this:

   

2. Place a piece of graph paper on the table between you and the compass. The lines on the graph paper should line up straight with the compass needle that still points to the right, like this:

   

   Not like this . . .

   

   or this:

   

3. Tape down the graph paper and the compass so they cannot move.
4. Push an end of one of the bar magnets close to the compass. Make sure the compass needle moves toward you. If it moves away from you, turn the other end of the magnet toward the compass and try again.
5. Let the compass needle settle back to 0. Place the magnet with its end exactly 4 squares on the graph paper away from the compass. Read and record the number the compass needle moves to.

   

6. Move the bar back another 4 squares. Read and record the number the needle moves to.Keep doing this until you run out of graph paper squares.

Stay Safe

Magnets won't hurt you, but they will destroy the information stored on the magnetic strip on banking and credit cards. Keep your magnets and your wallet well away from each other.

Go Easy

The "Go" procedure will work for you.

Go Far

You can hook small bar magnets together end-to-end. This allows you to test the distance effect using 2, 3, and 4 magnets. Create a mathematical statement from your data that relates the number of magnets to the distance effect.

Show Your Results

Put numbers in a data table like this for "Go" and "Go Easy":

For "Go Easy" and "Go," make bar or line graphs that show the relationship between distance and how far the compass needle moves. Display your materials so others can try the experiment for themselves.

For "Go Far," make separate data tables or add extra columns for the 2-, 3-, and 4-magnet combinations you test. Make line graphs that show the compass reading at different distances for 1, 2, 3, and 4 magnets. Use different color lines to show the result for each. Show your calculations and state any conclusions you drew about the relationship between numbers of magnets and distance.

Tips and Tricks

• If you can't find very small bar magnets like those shown here, you can substitute larger bar magnets you borrow from school or order from a scientific supply house. If your magnets are very large or very strong, however, you may need to modify the distances you test.
• You'll get some surprising results if you use button magnets for this experiment. Try it!

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