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Steering Science: Make a Homemade Compass

A physics project from Science Buddies


Use the Earth's magenic fields to make a homemade compass! 
George Retseck

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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