Magnetism - Point the Way
You know that Earth has both a north and a south pole. A very long time ago the Chinese discovered a way to use these poles to navigate. They found that if you put a rock called magnetite on a piece of wood and floated it in water, one end of the rock would always point to the North Star.
Sailors also used this tool, which we call a compass, to find their way while sailing on the oceans.
Today a compass needle is simply a thin, magnetized iron needle. The north point of a compass needle is attracted to the north pole and will always point north.
A compass is still a very useful and necessary tool for hikers, or anyone who needs to find his or her way. In fact, a compass played a very important part in the history of science.
You're the scientist!
Make a compass!
What do you think happens when a magnet is free to move in Earth's magnetic field? In this activity you will find out.
- Bar magnet
- Yarn (about twice as long as the bar magnet)
- Cut a length of yarn or string about twice as long as the bar magnet.
- Tie loops in both ends, and then put the bar magnet through both loops.
- Find the balance point on this harness where the bar magnet hangs level, and tie a longer piece of yarn or string there.
- Tie the other end of this string somewhere where the bar magnet can hang down and be left to swing on its own.
- What do you think will happen to the magnet? Write your hypothesis down.
- Observe the magnet. What happens? Record the results below.
- Can you explain what happened? Is the end of the magnet labeled "N" the north pole of the magnet? Explain your answer.