Byline
By Science Buddies
 
Key concepts
Magnetism
Navigation
Magnetic poles
Physics
Forces
 
Introduction
Have you ever used a compass to help you figure out what direction you should go? These can come in handy to help you navigate your way through a field or forest while camping, for example. Magnetic compasses work based on Earth's magnetic field. In this science activity you'll get to make your own magnetic compass. How well do you think it'll work? Get ready to find out!
 
Background
People have known about magnetism for thousands of years. Magnetism is the reason two magnets will push against one another or be pulled together. This can cause amazing things to happen, such as making an object hover above the ground because it is being pushed up by the magnetic force. Magnetism can also help people navigate; because Earth has a magnetic field, compasses can be made using a small magnetized bar or needle that points a certain direction (north or south) based on the field.
 
Although the phenomenon of magnetism has been known of for a couple thousand years, the first magnetic compasses used for navigation were not invented until relatively recently, approximately 1,000 years ago (sometime between A.D. 1000 and 1100). In this science activity you'll get to make your own compass, which may help you understand some of the challenges that early magnetic compass makers encountered!
 
Materials

  • Metal sewing needle
  • A magnet (It can be a flat refrigerator magnet or a more powerful magnet, such as a rare earth magnet—the most common type is made of neodymium—which can be purchased at many hardware stores. A stronger magnet will work best.)
  • A pair of pliers
  • A cork
  • Scissors for cutting the corkA wide cup, drinking glass or bowl
  • Water
 
Preparation
  • Be careful when handling the magnet, especially if you are using a strong magnet, such as a rare earth magnet. Keep the magnet away from other magnets and electronic devices, such as computers, cell phones and TV screens.
  • Use caution and have an adult help when you use the scissors to cut the cork and when you handle the needle.
 
Procedure
  • Rub the magnet against the sewing needle at least five times. (If you are using a weaker magnet, such as a flat refrigerator magnet, rub the needle at least a dozen times.) Always rub the magnet in the same direction against the needle. Your needle should now be magnetized.
  • Now cut off about one quarter inch of the cork from one of the ends, making a small cork disk that is about one-quarter-inch tall.
  • Laying the cork disk on a flat surface, carefully push the needle through the side of the disk by using the pair of pliers. Push the needle all the way through the disk so that about the same amount of needle shows on either side of the disk.
  • Fill a wide cup, drinking glass or bowl with at least one inch of water.
  • Put the cork disk (with the needle) on the water in the cup. Try to keep the disk floating in the center of the water, away from the sides of the cup. What does the needle do? When it stops moving, what direction does it point toward?
  • Does your homemade compass seem to work well? How is it limited in its use?
  • Extra: Find out what direction north is in your location. Did your needle point in that direction? (You can use a real compass, an atlas or smartphone map for this.)
  • Extra: Put a magnet next to your compass. What happens to the needle as the magnet is moved close to it? How close does the magnet need to be to affect the compass? You could also try this with a steel object (such as a nail or possibly the pliers).
  • Extra: If you have magnets with different strengths, such as a flat refrigerator magnet and a rare earth magnet, try making multiple compasses using the different magnets to magnetize the needles. How well do the different compasses work compared with one  another?
  • Extra: There are other ways you can make an inexpensive magnetic compass at home or while you are outdoors. For example, instead of using a piece of cork, you could try using a small leaf and setting the needle on top of the leaf while it floats in a still pool of water. How does a compass made using a leaf compare with one made using a piece of cork? How else could you make a magnetic compass?

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Observations and results
Did the needle in your homemade compass align itself along the Earth's north and south poles?
 
When you rubbed the magnet against the sewing needle, you magnetized the needle, effectively making it a weak, temporary magnet. Because magnets interact with one another (pushing against one another or pulling one another together), the magnetized needle can interact with Earth's magnetic field. Although Earth's magnetic field is relatively weak, it should have clearly affected the needle because the needle was allowed to freely float in the cork disk on the water. Specifically, once it stopped moving, the needle should have aligned itself along Earth's magnetic field, lining up along the north/south axis. This means that one end of the needle should have pointed north, while the other pointed south. The same end should have always pointed the same direction. (You can do some more research to figure out how to make a compass that always has the needle's tip point a specific direction—either north or south.)
 
More to explore
Fun Magnet Facts for Kids, from Science Kids
The Amazing Floating Train: How Much Weight Can a Maglev Train Hold?, from Science Buddies
Science Activities for All Ages!, from Science Buddies
Make Your Own Compass (pdf), from Discover Your World with NOAA

This activity brought to you in partnership with Science Buddies

Science Buddies