Academic journal article The Science Teacher

Invisible Field

Academic journal article The Science Teacher

Invisible Field

Article excerpt

1. Tape a magnet, like a diving board, to the bottom of an overturned cup.

2. Tie some thread onto a paper clip, and stick it on the end of the magnet.



3. Tape the thread to the table, leaving the end free.

4. Pull on the thread so the paper clip floats in the air!

5. Which inserted materials disturb the magnetic field ...

... index card?

... pin?

... another paper clip?

... aluminum foil?



To observe that a magnetic field passes through solid objects if they are not magnetic.


Photocopy the activity for each student or lab team.

Step 1. If the magnet makes the cup too top-heavy, tape it to the table.

Step 4. You can also "float" the magnet by sliding the cup slightly away. If the maximum resulting separation is not enough to pass test materials between, add a second magnetic increase the field strength.

Step 5. Magnetic lines of force pass undisturbed through nonmagnetic materials (paper, aluminum, plastic, glass), with no visible effect on the floating clip. …

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