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How to Rebuild a Compass

Compasses have been used for centuries to orientate maps and aid navigation. Building a homemade compass that can be dismantled and rebuilt makes for a science project that can introduce children to principles of physics. Compasses work by operating within the Earth's magnetosphere, an invisible force. Rebuilding a compass that has been used before demonstrates the consistency of this force. The Earth operates like a bar magnet that pushes or pulls the particles within charged materials.

Things You'll Need

Paper
Plastic bowl
Cork
Craft knife
Needle
Magnet

Instructions

- 1
  Place a piece of paper on a flat surface and position a plastic bowl in the middle of it. Mark the four cardinal points of the compass around the bowl. North should face south and east should face west. Lay a bottle cork sideways on a protective piece of material or workbench. Use a craft knife to cut about a 1/2-inch off the cork.
- 2
  
  Use only one end of a U-shaped magnet.
  
  Magnetize your compass by holding a sewing needle in one hand at the end. Swipe it with a magnet from the end you are holding to the point of the needle. Do not swipe back down the needle, but return the magnet to the start position and swipe to the point of the needle once more. Make about 40 swipes in the same direction down your needle.
- 3
  Push the needle through your section of cork sideways so that the needle extends at either side of the cork an equal amount. Push it into the rounded edge of the cork, rather than the flat side that you cut.
- 4
  Pour enough water into the plastic bowl so that the cork and needle float freely on the surface. Place the cork and needle into the water. The needle will be attracted to north. Adjust the paper under the bowl to show north in the same direction the needle is pointing.
- 5
  Dismantle your compass by pouring away the water and removing the needle from the cork. When you want to rebuild your compass, remember to magnetize the needle again with a few swipes of your magnet and place it back into the bowl of water.

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