Natural Science Unit 30 Laboratory Activity: Magnetism

Goal: To determine the extent of a magnet's local field.

Materials and Equipment:

1. Large sheet of paper
2. Compass (several if possible)
3. Two or more small bar magnets

Procedures:

• Leave the small magnet in another room and find a place where your compass seems "true", that is, where it points toward the magnetic north point for your location. We don't want localized magnetic interference from electrical equipment or the refrigerate to skew your results.
• Place the large sheet of paper flat on a table in this area.
• Put your smallest bar magnet on the table in any orientation except one aligned with the earth's magnetic field.
• Place your compass on the paper within one inch of the magnet. Place a dot on the paper next to the position of the "north" end of the compass needle and a square next to the "south" end of the compass needle.
• Move the compass out of the way and draw a line from the square to the dot; put an arrow pointing along the line toward the current magnetic field's "north".
• Map at least 25 different points around your magnet this way, gradually moving out further from the compass. You are mapping the lines of force due to the small magnet.
• As you move out, you should notice the compass start to point again in the direction of the earth's magnetic field. Draw a line around the magnet at this distance. This is the extent of the magnet's "field of influence".
• Repeat the experiment with at least one other magnet of a different size or shape from the first.

Report:

Your report should include:

• A description of your materials and procedure.
• The distance at which each magnet loses its influence over the compass.
• An analysis of which magnet is stronger, based on its ability to counter the earth's magnetic field.

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