1202_LabManual.pdf

# Write down a measurement plan m easurement based on

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Write down a measurement plan. M EASUREMENT Based on your exploration, choose a scale for your graph of magnetic field strength against position that will include all of the points you will measure. Use the Hall probe to measure the magnitude of the magnetic field along the axis of the coils of wire. Be sure to measure the field on both sides of the coils. What are the units of your measured magnetic fields? How do these compare to the units of your prediction equations? Use the DMM to measure the current in the two coils. As a check, repeat these measurements with the other current configuration. If you are not familiar with a DMM, see the Equipment appendix. Pay special attention to the connections and settings that are used to measure voltages and currents, and why the DMM should be connected in the circuit differently for voltage and current measurements. Do you know why we should connect them in these ways? A NALYSIS Graph the measured magnetic field of the coil along its axis as a function of position and compare to your prediction. C ONCLUSION For two large, parallel coils, how does the magnetic field on the axis vary as a function of distance along the axis? Did your measured values agree with your predicted values? If not, why not? What are the limitations on the accuracy of your measurements and analysis? Does this two-coil configuration satisfy the requirement of giving a fairly uniform field? Over how large a region is the field constant to within 20%? This very useful geometric configuration of two coils (distance between them equals their radius) is called a Helmholtz coil. 143

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