From its behavior determine if this is caused by a

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Unformatted text preview: er along the axis of the loop or somewhere else? Set up your Hall probe as explained in the Equipment and Software appendices. Before you push any buttons on the computer, locate the magnetic field strength window. You will notice that even when the probe is held away from obvious sources of magnetic fields, such as your bar magnets, you see a non-zero reading. From its behavior determine if this is caused by a real magnetic field or is an electronics artifact or both? If you notice an ambient field, can you determine its cause? 136 CURRENT CARRYING WIRE – 1302Lab5Prob2 Go through the Hall probe calibration procedure outlined in the appendix, or in the Magnetlab Guide Box in the upper right corner of the application. Be sure the sensor amplification switch on the Hall probe is set to 6.4mT range. The MagnetLab application requires the probe to be set to the 6.4mT range to work correctly. Does the Hall probe ever read a zero field? Hold the Hall probe next to the wire; how can you use the information from your compass to decide how to orient the probe? Read the value displayed by the MagnetLab program. What will happen when you move the probe further from the wire? Will you have to change the orientation of the probe? How will you measure the distance of the probe from the wire? MEASUREMENT Use your measurement plan to create a map of the magnetic field around the stretched wire and the looped wire. Include the magnitude and direction of the magnetic field for each distance. ANALYSIS The direction of the magnetic field at a point near a current-carrying wire can be found by using the "right-hand rule" that is described in your text. How does the "right-hand rule" compare to your measurements? CONCLUSION How did your predictions of the map of the magnetic field near current-carrying wires compare with both physical and simulated results? How do they compare with the "right-hand rule"? 137 CURRENT CARRYING WIRE – 1302Lab5Prob2 138 PROBLEM #3: MEASURING THE MAGNETIC FIELD OF PERMANENT MAGENTS Your team is designing a probe to investigate space near Jupiter. One device uses strong permanent magnets to track the motion of charged particles through Jupiter’s magnetic field. You worry that their magnetic fields could damage computers on the probe. To estimate how close a magnet can be to a computer without causing damage, you have been asked to determine the magnitude of the field near the magnet. No isolated magnetic monopoles have ever been discovered (a difference between magnetism and electricity) but you wonder how accurately one could mathematically model the field of a bar magnet as the vector sum of fields produced by monopoles located near each end of the magnet. With this model, you calculate how the magnetic field would vary with distance along each symmetry axis of a bar magnet. You assume that a magnetic monopole would produce a magnetic field similar to the electric field produced by a point charge. To test your model, you decide to measure the magnetic field near a bar magnet with a Hall probe. 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. Review your notes from the earlier problem: Electric Field from a Dipole EQUIPMENT You will have a bar magnet, a meter stick, a Hall probe and a computer data acquisition system. You will also have a taconite plate and a compass. Read the section The Magnetic Field Sensor (Hall Probe) in the Equipment appendix. Read the section Measuring Constant Magnetic Field in the Software appendix. 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. WARM UP 1. Draw a bar magnet as a magnetic dipole consisting of two magnetic monopoles of equal strength but opposite sign, separated by some distance. Label each monopole 139 MEASURING THE MAGNETIC FIELD OF PERMANENT MAGNETS – 1302Lab5Prob3 with its strength and sign, using the symbol “g” to represent the strength of the monopole. Label the distance. Choose a convenient coordinate system. 2. Select a point along one of the coordinate axes, outside the magnet, at which you will calculate the magnetic field. Determine the position of that point with respect to your coordinate system. Determine the distance of your point to each pole of the magnet, in terms of the position of your point with respect to your coordinate system. 3. Assume that the magnetic field from a magnetic monopole is analogous to the electric field from a point charge, i.e. the magnetic field is proportional to g/r2 where...
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