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Pointer: How Does A Compass Work?

based on 9 ratings
Author: Janice VanCleave

Problem

How does a compass work?

Materials

  • compass

Procedure

NOTE: Never touch a compass with a magnet. Touching a compass with a strong magnet can change the polarity of the compass needle, causing the end marked north to become a south pole and all directions to be reversed.

  1. Place the compass on a wooden table away from magnets or magnetic materials.
  2. Observe the compass needle and determine which end is the north pole. The north end of the needle will have some distinguishing mark, such as an arrowhead or a color.
  3. Printed on the compass are the letters N, E, S, and W, which represent the directions north, east, south, and west Turn the compass on the table until the letter N is even with the north pole of the compass needle.

Results

The compass needle points north. The printed letters on the compass indicate the directions east, south, and west

Pointer

Why?

A compass is an instrument used to determine directions by means of a magnetic needle that always points to the earth's magnetic north pole. The main part of a compass is its magnetized needle. This needle is balanced so that when the compass is held horizontally, the needle can swing around freely. The magnetized needle acts like any bar magnet with both a north and a south pole. The needle swings into a north-to-south position as the poles of the magnetic needle line up with the magnetic lines of force around the earth. All the compass directions are easily determined when the compass is positioned with the north pole of the needle pointing to the N printed on the compass.

Let's Explore

  1. Would the compass work if you held it in your hand? Repeat the experiment, holding the compass in a horizontal position.
  2. Does it matter where you stand while holding the compass? Repeat the original experiment in different rooms, as well as at different places outside. Science Fair Hint: Diagrams with instructions for how to work a compass can be used as part of a project display.
  3. Pointer

  4. What effect would a magnet or a magnetic material have on the compass? Repeat the original experiment by placing a magnet or a magnetic material, such as a paper clip, near but not touching the compass.

Show Time!

Make and display different kinds of compasses.

  • A nonmagnetic compass clock can be constructed by drawing the face of a clock on a paper circle. Place the paper on an outside surface in direct sunlight. Stick a pin in the middle of the circle and turn the paper until the shadow of the pin falls on the correct time. NOTE: Do not use daylight savings time, because during daylight savings time your solar clock will read one hour earlier than your watch. North will always be halfway between the shadow and the number 12 on the paper clock.
  • You can also make a floating compass. Cut a paper ring to fit around the outside of a bowl. Mark the four compass directions N, E, S, and W on the paper ring. Fill the bowl with water. Cut a 1-inch × 1-inch (2.5-cm × 2.5-cm) piece from a sponge. Place the sponge piece in the water and lay a magnetized needle on top of it. (To temporarily magnetize the needle, lay it on a bar magnet for two minutes with the eye of the needle at the north end of the magnet.) The needle and the sponge will swing around so that the point of the needle faces north. Rotate the paper collar around the bowl so that the point of the needle points to the N on the paper.

Pointer

Check It Out!

In the 12th and 13th centuries, Arabian and Chinese astronomers discovered that magnetic stones suspended from strings always turned toward the same direction. In the 14th century, European navigators began to explore the oceans with reasonable assurance that they could find their way back home with the aid of a magnetic compass. Find out more about compasses. Discuss information such as:

  • what makes a mariner's or a ship's compass special.
  • types of magnets used in the past and in the present.
  • uses of compasses in our modern technological world.
  • how a gyrocompass works.
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