We made an electromagnet—not a particularly
strong one—by winding some 32-gauge magnet wire 100 times
around some plastic pipe, and then put a steel bolt inside the pipe.
Then we suspended that setup over a small permament magnet that
was strapped to a Vernier force probe. The two magnets attracted
one another, so our reading is the (upward) pull on the probe.
We zeroed the probe before bringing the electromagnet into the
picture (but the zeroing compensates for the weight of the permament
height is the distance between the electromagnet
and the permanent magnet in centimeters.
current is the current through the electromagnet
force is the force in Newtons, the pull on the
How does the force depend on the current?
If you fit a line to the force-current data, what do the slope
and intercept mean?
Why is there a force reading when the current is zero?
How does the force depend on the distance? (and how does this relate
to the other magnetism exhibits in the zoo?)
(data by Bryan Cooley, Jan 2003)