Universe Cycle - Geography (1)
 Lab 

   
OBJECTIVES:
  • Exploring how to use a compass.
  • Discovering how to find directions.
VOCABULARY:
  • compass
  • east
  • north
  • south
  • west
MATERIALS:

Students learn to read a compass.

BACKGROUND:

Geophysicists theorize that circulation of molten metal in the Earth’s outer core generates the Earth’s magnetic field. At the present time, the field is oriented so that the north end is positive, and the south end is negative. These are called, respectively, the North and South Magnetic Poles. They are not the same as the geographic poles, which mark then ends of the Earth’s rotational axis. The magnetic poles actually move around constantly. It is easiest to say that the Magnetic North Pole is near the geographic North Pole.

The compass is a device that helps us locate north and south. A compass consists of a small needle which is free to swing horizontally. A small magnet is attached on one end of the needle and the other end is balanced so the needle swings easily. The magnet pulls the needle to line up with the Earth’s magnetic field. One end of the needle (often colored red) thus points north, while the other end points south. Once the needle points to north, you move the North position on the compass to coincide with the needle. Then you can see the directions easily.

PROCEDURE:
  1. Ask the students which way is north. Many will say "up," as if the north pole is in the sky. Describing the direction of the north pole is difficult, because north, in and of itself, describes location.

    Give each student or student group an inflatable globe. Have them put a "post it" sticker with a "N" on it on the North Pole and an sticker with an "S" on the South Pole.

    Ask them again if north is up. It should now be clearer to them that north and south are directions on the Earth’s surface.
     

  2. Give each student or student group a compass. Explain how the compass works. Review the notation on the compass. Let them experiment with them briefly, learning that the needle always points the same direction.
      
  3. Give each student or group a bar magnet, and have them experiment with the compass and magnet. Tell them which side of the magnet is north and which is south. The needle will line up with the north end of the magnet. This works on the same physical principle as the Earth’s magnetic field. However, the local magnetic field of the magnet is stronger than the Earth’s magnetic field, so the compass "feels" it more and lines up with it. Discuss why this happens with the class.
     
  4. Now that the students have found North and South, tell them that East is half way between North and South on the right side of the compass, and that West is half way between North and South on the left side.

    Have the students put the compass on the worksheet where it is labeled "compass." Have the students put the bar magnet at each of the lines, with the North end point outward. Go over what happens, and why, at each position.
     

  5. Ask the students from what direction the Sun appears to rise (the East). Ask them if they can use this knowledge to find North, West, and South. Go over this carefully with the students. West would be directly opposite east. North would be left of east-west line and south would be right of the east-west line. Ask the class in what direction the Sun sets (the West). Ask them what direction the Sun moves in the sky (East to West).
      
  6. You may want to go outside to find where north and south are located from the school. Ask students, in what direction the Sun rises? That is the first clue of east. Where does the Sun set? In the west. They can figure north and south from these two pieces of observation. So students can locate the general direction without a compass.

Note: be sure to store the compass and magnets separately, so as not to demagnetize the compasses. A compass works best outside, when there is no interference of electricity or metal.

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