Measure the field on both sides of the coil be sure

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Unformatted text preview: ll probe without introducing additional uncertainty to your measurement? 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 averaging. 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 R R 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 Equipment appendix. 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 labhelp@physics.umn.edu. 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.

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