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Day 2: Design and Build a Magnetometer
Student Pages

We are going to build a device for detecting the presence of a magnetic field: a magnetometer. We will use a magnet as the 'sensor', attach it to a small card, and hang it from a thread in a jar. We will conclude by testing the magnetometer with various materials.

Materials for each student:

• 1 clear, wide mouth, plastic jar with screw on lid
• 3 feet of sewing thread
• 1 small bar magnet
• 1 piece index card
• 1 piece of soda straw
• Glue

Procedure:

1. Clean the jar thoroughly and remove labeling.
2. Pierce a small hole in the center of the cap.
3. Glue the magnet to the center of the top edge of the card.
4. Label the ends of the magnet by marking the card. We suggest using designations like "A" and "B" such that all A's attract all B's.
5. Glue the piece of soda straw to the top of the magnet.
6. Thread the thread through the soda straw and tie it into a small triangle with 2 inch sides.
7. Tie remaining thread to the top of the triangle in #7 and thread it through the hole in the cap.
8. Put the jar top and bottom together so that the 'sensor card' is free to swing in response to the magnetic fields.
9. Glue the thread through the cap in place.

Practice Using the Magnetometer:

Work with the magnetometer and materials provided to you. Answer the following questions. Cite your test procedure, evidence, and the reasoning that supports your answer.

• What is the magnet in the bottle sensing?

• How long must you wait after placing magnetometer to get a reliable orientation observation?

• How does rotating the bottle while making an observation affect the reliability of the measurement?

• How does your presence in the vicinity affect the reliability of the measurement?

• Can non-magnetic materials cause deflections?

• How far must one magnetometer be from another in order to keep them from interfering?

Lesson Development/Writing: Ed Eckel
Web Design: Theresa Valentine
Last Updated: 8/15/2000