Purpose: Investigate how the strength of the field is
affected by the number of coils per unit length in a coil.
Qualitatively explain why this relationship makes sense. Why
should it be true that twice as many coils in a given length results
in the corresponding change in magnetic field.
Extensions: A further investigation might be to see how
the field strength is related to the diameter of the coil. You
could use different size slinkies or springs with the same number
of coils and see how the field changes with current level. Be
sure to compare it to a coil with the same number of coils per
Qualitatively and Quantitatively Map the Field. Place butcher paper under the coil and use the probe to measure the field at different locations in the coil, at its ends, and in regions surrounding the coil. Also place the probe at different angles. Remember the probe must be perpendicular to the field so at the ends try rotating the probe and look for the maximum reading at a location.
Sample data taken from a CBL, entered in Excel and graphed. Similar
data was taken using a computer interface, but no advantage in
using this method appeared in the data.
Written by Christine Deyo, July 1997