Investigating the Magnetic Field in a
Purpose: Investigate how the strength of the field is
affected by the current flowing in a coiled wire.
- Select a slinky and stretch it between two cardboard supports.
Do not over stretch the slinky!!
- Connect a DC power supply to the ends of the slinky.
- Insert a Multi-meter into the circuit and connect it to measure
- Count the number of coils between the cardboard supports and
record this value.
- Measure the distance between the supports.
- Assemble the CBL, TI-82, and magnetic field sensor: be sure
that all cables are firmly and gently in place.
- Support the sensor and place it in the center of the slinky.
- Use the PHYSICS program in the calculator to collect data.
Use the High(mTesla) setting and collect data with choice #3;
- Use the power supply to vary the current and record the magnetic
field strength in L1 as you collect your data. Don't forget to
record the current level for each reading.
- Construct a graph of Current vs. Magnetic Field Strength.
You may download L1 using the graph link or enter the data in
a spreadsheet or graph on your calculator.
- Find the equation that describes the relationship between
Current and Magnetic Field Strength. Remember that y and x may
not be used as variables and that units must accompany all constants.
What is the meaning of the y-intercept and the slope of this
- Qualitatively explain why this relationship makes sense.
Include an explanation of what current means and why doubling
the current causes the resultant change in magnetic field strength.
Teacher Notes: I used the CBL to collect data but it could
be collected on any computer interface. I also took data with
an MPLI unit but found no advantage to collecting in this manner.
Sample data taken for current vs magnetic field. It was collected
with a CBL, entered into a spreadsheet on Excel and graphed.
This data could also be analyzed easily on the TI-82. Using the
suggested program, the Field data is already stored in L1 and
the coil / length could be calculated as it is added to a second