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Unformatted text preview: Magnetic Force on a Current Wang Zhikai (A0080959N) Group B6 Pc1222 Lab Report: Magnetic Force on a Current 1 Objective of Experiment Investigate how the magnetic force on a current carrying wire is related to current, length of wire and the magnetic field strength. Determine experimentally the magnetic field strength of the magnets used. 2 Introduction When a charged particle moves with velocity v across a uniform magnetic field B , it experiences a magnetic force of magnitude | F | = q | v || B |sin , where q is the amount of charge on the particle and is the angle between the direction of the particles velocity and the direction of the magnetic field. Knowing either two out of the direction of the velocity, magnetic field and magnetic force can allow us to find out the third using the right-hand rule. For a current flowing in a wire, the magnitude of the magnetic force acting on the current-carrying wire is | F | = I | l || B |sin , where I is the magnitude of the current and l is the vector length of the wire that points in the direction of I . In this experiment, the magnetic force is measured by means of a force-on-a-conductor balance. A rider is used to balance out the magnitude of the magnetic force. The distance of the rider from the pivot, x , is used to calculate the magnitude of the magnetic force using the following equation: F = mg , where y is the distance of the wire BC from the pivot, m is the mass of the rider and g is the gravitational field strength of the Earth. The purpose of this experiment is to investigate if the relationship between the magnitude of the current and the magnitude of the magnetic force, the relationship between the length of the current-carrying wire and the magnitude of the magnetic force as well as the relationship between the number of magnets used to produce the magnetic field that produces the magnetic force and the magnitude of the magnetic force. We can then determine if our experimental results deviate from the results predicted by the two equations | F | = I | l || B |sin and F = mg . We will then be able to analyse the factors that caused the deviation, if any. 3 Methodology Part A: Force versus Current Our purpose is to investigate the 2 variables (force and current) involved in the equation | F | = I | l || B |sin . We recorded the mass of the rider and the distance of the wire BC from the pivot. We then placed 5 magnets with the poles with black dot-mark on the same pole piece such that they overlap with the end section of wire BC completely. The rider was put at zero position of the scale and with no current flowing through BC, we balanced the beam with the zero adjustment mass so that the wire loop was horizontal. We turned on the DC power supply and adjusted the voltage output to 5V. We ensured this reading was kept constant throughout the experiment and rubbed off any carbon accumulated on the pillars with an eraser....
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- Spring '11