Use the vector cross product calculate the motion of

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Unformatted text preview: ght current-carrying wires, and coils of wire. • Calculate the magnetic force on a charged particle moving in a uniform magnetic field and describe its motion. PREPARATION: Read Tipler & Mosca: Chapter 26, sections 1-4 and Chapter 27.1. Review your notes from the first lab (Electric Fields and Forces). Before coming to lab you should be able to: Add fields using vector properties. Use the vector cross product. Calculate the motion of a particle with a constant acceleration. Calculate the motion of a particle with an acceleration of constant magnitude perpendicular to its velocity. Write down the magnetic force on an object in terms of its charge, velocity, and the magnetic field through which it is passing. 129 LAB 5: MAGNETIC FIELDS AND FORCES 130 PROBLEM #1: PERMANENT MAGNETS You have a job working at a company that designs magnetic resonance imaging (MRI) machines. The ability to get a clear image of the inside of the body depends on knowing precisely the correct magnetic field at that position. In a new model of the machine, the magnetic fields are produced by configurations of permanent magnets. You need to know the map of the magnetic field from each magnet and how to combine magnets to change the magnetic field at any point. You decide to determine the form of the magnetic field for various combinations of bar magnets, and to draw vector diagrams (field maps) for each combination. 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 26 Section 1. EQUIPMENT You will have two permanent magnets, a magnetizer (if needed) and a clear plate filled with a viscous liquid and particles of taconite. When a magnet is placed on top of one of these plates, the Taconite pieces align themselves with the magnetic field. You will also have a compass. The magnet configurations you need to consider are as follows: Read the section Magnetizing a Bar Magnet in the Equipment appendix if you need to remagnetize your magnets. 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. 131 PERMANENT MAGNETS – 1302Lab5Prob1 WARM UP 1. Make a sketch of all the magnets in each figure. Be sure to label the poles of the magnets. 2. Choose a point near the pole of a magnet. At that point draw a vector representing the magnetic field. The length of the vector should give an indication of the strength of the field. Keep in mind that: The field can have only one value and direction at any point. The direction of the magnetic field points away from a North pole, and towards a South pole. The field at a point is the vector sum of the fields from all sources. 3. Move a short distance away in the direction of the vector and choose another point. At that point draw another magnetic field vector. Continue this process until you reach another magnetic pole. Choose another point near a pole and start the process again. Continue until you can see the pattern of the magnetic field for all parts of the configuration. PREDICTION Sketch a map of the magnetic field for each magnet configuration in the figures in the equipment section. Assume that the different magnet configurations in each figure do not interact with the magnets in the other figures. EXPLORATION WARNING: The viscous liquid (glycerin) in the Taconite plate may cause skin irritation. If a plate is leaking, please notify your lab instructor immediately. Check to make sure your Taconite plate is not leaking. Gently shake the plate until the Taconite is distributed uniformly (the transparent bar inside the plate will help redistribute the flecks when moved). Properties of magnets can change with handling. Check the poles of the magnet with your compass. Inform your lab instructor if the magnet does not behave as you would expect, a magnetizer can be used to correct the polarity and intensity if necessary. 132 PERMANENT MAGNETS – 1302Lab5Prob1 Place a permanent magnet on the Taconite plate. If the flecks are difficult to see, put a piece of white paper behind the plate. How long must you wait to see the effect of the magnetic field? Is it what you expected? Try some small vibrations of the Taconite plate. How does the pattern in the Taconite relate to the direction that a compass needle points when it is directly on top of the Taconite sheet? Try different configurations of magnets and determine how to get the clearest pattern in the Taconite. What can you do to show that...
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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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