Thomas FarleyLee GroenewegEGR 345 Lab 7a Magnetic DampingMike ZandstraThomas FarleyLee GroenewegOctober 28, 1998Purpose: To observe magnetic damping using Neodymium magnets.Theory: As we move a continuous mass of metal into a steady (static – no-time varying) magneticfield, an electric current (due to electron flow) will be induced on the metal. If we move faster, then the current will be greater, but the motion will be over faster, resulting in the same net energy. In this lab we start with the idea of moving metal in a magnetic field. But, if we keep the metal still and move the magnet we can get a similar effect. In this labwe will drop a magnet down a copper tube. The tube will allow the currents to flow fully and as a result a strong opposing field will be setup. The magnet will be pulled downwardby gravity and pushed upward by the magnetic field as it drops down the tube. And, because this effect is proportional to velocity the resistance force will be act as a dampingforce.Equipment:- Computer with LabVIEW (PSE Dell 123)- copper tube (#27)- Neodymium Magnet- Masses (to be attached to magnet)- Miscellaneous wires and clips used in circuit to collect data with LabVIEW.Procedure:For the first procedure of this lab, we measured our magnets, the masses we were going to use and the length between the signaling points on our tube. For the second procedure, we needed to develop a system in LabVIEW to collect the data, which was used to determine the velocity of the magnet, and the damping coefficients in the copper tube. Since we were not able to see when the magnet passed the electrical terminals on the tube, we needed to develop a way to record the data as the mass was dropped through the tube. In the second procedure we designed a system in LabVIEW to collect the data and write it to a file. This was accomplished using the Do-While loop function in LabView that we configured to write data to a text file at increments of 100 milliseconds. The data in the text file was then converted into an Excel format to reproduce the graphs we observed with LabVIEW. The Do-While Loop system we developed is shown in figure 1.Figure 1. LabVIEW Do-While Loop used to collect data.After the Do-While Loop was created, we passed the magnet through the tube to ensure that the system was working correctly. Once we were confident that the system was collecting data properly, we began to drop the magnet through the tube and collect data. We passed the magnet through the tube three times so that we could obtain data with a minimal amount of error. We then added a mass to the magnet and dropped it through the tube. We passed this assembly through the tube three times also.We then added another mass to the magnet and dropped it through the tube three times.The addition of the masses to the magnet was to determine the damping coefficient. The damping coefficient can be found using the following equation:ydtdMydtdKMgFdy2(1)where,It is important to note that in the equation the mass reaches terminal velocity almost immediately. This results in the assumption that the acceleration of the mass is negligible.The masses for the three magnet assemblies are found in table 1.Magnet Only 6.00 gramsMagnet+Mass 1 9.45 gramsMagnet+Mass 2 13.10 grams Table 1. Masses for magnets and additional massesThe graphical outputs (in Excel format) for the magnet passing through the tube are attached as Appendix A, B, and C. We were also to calculate the damping coefficient using Equation 1. The data calculations for velocity and damping coefficient are attached as Appendix D.Discussion: The results for the mass-velocity relationship appear to be linear. As for the effects of magnetic damping on the mass, it slows the mass’s velocity down significantly.Conclusion: This lab required us to use our previous knowledge from using LabVIEW to develop a system for collecting data. This required us to experiment with the different capabilities of LabVIEW. This experimentation allowed us to learn more about LabVIEW and all that it can offer us in our learning experience, and in other situations we may encounter. The design aspect of this lab was beneficial to our learning as engineers in how to approach problems that there may be more than one solution to. This lab also introduced us to another system in the real world that we are able to use the material learned in the classroom to
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