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Magnetic Field Strength & Distance

Objective: To determine how magnetic field strength varies with distance.

Materials: Macintosh or IBM - compatible computer, Serial Box Interface or ULI, Logger Pro, Vernier Magnetic Field Sensor, Meter Stick, Disk shaped Neodynium magnet.



1. Place the magnet at the end of the meter stick. Place the magnetic field sensor at the 1 centimeter mark. The sensor should be set on its low setting. The white dot on the sensor should be facing toward the magnet.

2. Prepare the computer for data collection by opening "Exp 27a" from the "Physical Science with Computers" experiment files of Logger Pro.

3. Click on "Collect" to begin taking data. When the reading has stabilized, click "keep". Type "1" in the edit box. Press enter. The magnetic field strength at a distance of 1 cm is now saved.

4. Move the sensor down the meter stick in 1 cm increments until the 10 cm mark and record the field strengths at each distance.

5. Click "stop" to end data collection.


1. Try to fit a curve onto your data then print your graph.

2. How does magnetic field strength vary with distance?

3. Each electrical appliance you use has current running through it. This current generates a magnetic field. Suppose you are standing a certain distance from your TV set. If you now move to twice that distance, is the magnetic field stronger or weaker? By how much?

Sample Data & Graph:

Extensions: If you have access to CBLs, you could have students measure themagnetic fields near a variety of electrical appliances.