182 the magnitude of the induced potential difference

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Unformatted text preview: ugh the ring, and when it has? Will the peaks be sharp or rounded? Will there be many peaks or only one? How will the signal look different from background noise? Draw on your experiences from problems 1 and 3 in this lab. Plug the voltage probe into the SensorDAQ interface using the required Ch. 1. Attach the clips to the two ends of the coil and start the VoltageTimeLab program. Make sure you read the software appendix if necessary. 182 THE MAGNITUDE OF THE INDUCED POTENTIAL DIFFERENCE – 1302Lab6Prob4 Push the bar magnet through the coil to make sure that the apparatus is working properly and that you are getting appropriate signal on the screen. How does the graph compare to your expectations? Make sure you can freeze the screen while showing your desired data. Set up the track at an incline so that a rolling cart will go through the center of the coil. Try different angles to get the most reproducible situation in which you can change the velocity of the cart over the widest range without damaging the equipment. Be sure to have someone catch the cart when it reaches the end of the incline. Securely attach a bar magnet to the cart and let it roll down the track while observing the potential difference displayed by the computer. Check that the release position does affect the potential difference graph on the computer. Try different time scales over which the computer makes the measurement. Are the differences large enough to measure reliably? Does the orientation of the magnet matter? Try different orientations. Do the magnetic bumpers in the cart matter? Try a cart without a bar magnet. Does the display of the potential difference as a function of time on the computer look as you expected? Be sure you can qualitatively explain the behavior that you see displayed. You might want to move the magnet by hand to see if your understanding is correct. Try adding another bar magnet to the cart to increase the magnitude of the induced potential difference. Does it matter how the second magnet is oriented? Develop a measurement plan to take the data you need to answer the question. MEASUREMENT Follow your measurement plan and record the maximum potential difference across the ends of the coil of wire as a function of the velocity of the magnet through the coil. ANALYSIS From your data construct a graph of maximum induced potential difference in the coil as a function of the distance from the coil at which the cart is released. Add the graph of your prediction to the same plot and compare. You may need to normalize the graphs. 183 THE MAGNITUDE OF THE INDUCED POTENTIAL DIFFERENCE – 1302Lab6Prob4 CONCLUSION Did your results agree with your predictions? Explain any differences. From the computer screen, make a sketch of the shape of the induced potential difference across the ends of the coil as a function of time for one pass of the magnet. Label each feature of the graph and indicate where the magnet is in the coil at that time and why the graph looks like it does at that time. 184 PROBLEM #5: THE GENERATOR To begin investigating how to improve the efficiency of electric generators, your supervisor assigns you the task of building a working model of a generator from which it is easy to take measurements. Your model consists of Helmholtz coils to generate a well-defined magnetic field and a smaller coil of wire, in between the Helmholtz coils, to generate the current. The small coil is mounted to a motor so that it spins at a uniform speed. Before presenting the model to your supervisor you calculate the potential difference you expect and then take some measurements to make sure that the results correspond to your understanding of the situation. You will need to determine how the expected potential difference may depend on time, the rate of small coil rotation, and other parameters in your setup. 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 28.4. EQUIPMENT The small coil mounts to the base between the Helmholtz coils, as shown to the right. The Helmholtz coils are connected to a power supply. The small coil is labeled with the # turns of wire, and can be rotated by a motor. DO NOT connect a power supply to the small coil or you will damage it. You will have a Hall probe, a DMM, and a meterstick. You will also have a voltage probe with the VoltageTimeLAB software. s mall coil Helmholz coils Read the sections The Magnetic Field Sensor (Hall Probe) & The Digital Multimeter in the Equipment appendix. Read the sections Volta...
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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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