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Write down a measurement plan. MEASUREMENT
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 and direction of the magnetic field as a
function of position along the axis of the coil. Measure the field on both sides of the
coil. Be sure your Hall probe is calibrated and has the correct orientation to accurately
measure the magnetic field. Make sure you take at least two measurements for
Use the Hall probe to complete the field map for the coil.
Use the DMM to measure the current in the coil. Try measuring the field along the axis
at several different currents.
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?
Don't forget to measure the diameter of the coil and record the number of turns. What
considerations need to be made when measuring the diameter? ANALYSIS
Graph the measured magnetic field of the coil along its axis as a function of position
and compare with your prediction. CONCLUSION
Does the graph of magnetic field strength as a function of distance agree with your
prediction? Is this true everywhere? Why or why not? 152 PROBLEM #6: MEASURING THE MAGNETIC FIELD
OF TWO PARALLEL COILS
You have a part time job working in a laboratory developing large liquid crystal
displays that could be used for very thin TV screens and computer monitors. The
alignment of the liquid crystals is very sensitive to magnetic fields. It is important that
the material sample be in a fairly uniform magnetic field for some crystal alignment
tests. The laboratory has two nearly identical large coils of wire mounted so that the
distance between them equals their radii. You have been asked to determine the
magnetic field between them to see if it is suitable for the test. You decide to make a
graph of the field strength along the axis of the coils.
Instructions: Before lab, read the laboratory in its entirety as well as the required reading in the
textbook. In your lab notebook, respond to the warm up questions and derive a specific prediction
for the outcome of the lab. During lab, compare your warm up responses and prediction in your
group. Then, work through the exploration, measurement, analysis, and conclusion sections in
sequence, keeping a record of your findings in your lab notebook. It is often useful to use Excel to
perform data analysis, rather than doing it by hand.
Read: Tipler & Mosca Chapter 27 Section 2 and Example 27-2. EQUIPMENT
You have two 200 turn coils, a base, banana wires, and
an 18volt/5amp power supply. The coil base has
markings showing correct spacing for a uniform field. I I
x You also have a digital Multimeter (DMM), a compass,
a meter stick, and a Hall probe. A computer is used for
data acquisition with the MagnetLab program.
Read the sections The Magnetic Field Sensor (Hall Probe) & The Digital Multimeter in the
Read the section Measuring Constant Magnetic Field in the Software appendix.
Read the appendices Significant Figures, Review of Graphs and Accuracy, Precision
and Uncertainty to help you take data effectively.
If equipment is missing or broken, submit a problem report by sending an email to
email@example.com. Include the room number and brief description of the
problem. 153 MEASURING THE MAGNETIC FIELD OF TWO PARALLEL COILS – 1302Lab5Prob6 WARM UP
1. Draw a picture of the situation showing the direction of the current through each
coil of wire. Establish a single convenient coordinate system for both coils. Label
all of the relevant quantities.
2. Select a point along the axis of the two coils at which you will determine an equation
for the magnetic field. In the previous problem, you calculated the magnetic field of
one coil as a function of the position along its axis. To solve this problem, add the
magnetic field from each coil at the selected point along the axis. Remember to pay
attention to the geometry of your drawing. The origin of your coordinate system for
this problem cannot be at the center of both coils at once. Also remember that the
magnetic field is a vector.
3. Use your equation to graph the magnetic field strength as a function of position
from the common origin along the central axis of the coils. Describe the qualitative
behavior of the magnetic field between the two coils. What about the region outside
the coils? PREDICTION
Calculate the magnitude of the magnetic field for two coils as a function of the position
along their central axis, for the special case where the distance between the coils is the
same as the radius of the coils. Use this expression to graph...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.
- Spring '14