E/M Ratio - The e/m Ratio of the Electron Abstract In the...

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The e/m Ratio of the Electron Abstract In the study of the Charge/Mass Ratio of the Electron, experiments were performed to obtain two main goals. The first goal was to examine the formation of magnetic fields produced by a bar magnet, a solenoid, and a set of Helmholtz coils. These magnetic fields were then mapped out. The second goal was to measure the e/m ratio of electrons. In the experiment involving the bar magnet, using a compass, the magnetic field was mapped out. This map depicted the movement of magnetic field lines originating from the North Pole and extending to the South Pole, with the strongest density of field lines at either pole. The experiments involving the solenoid and the Helmholtz coils acted similar to the bar magnet. In the case of the solenoid, its magnetic field was mapped twice as the polarity of the electric current running through the solenoid was reversed. Through mapping it was found that a uniform magnetic field was produced within the solenoid. With the Helmholtz coils, a uniform magnetic field was created. Using a Hall Effect probe, the maximum positive value observed within the Helmholtz coils was found to be 25.1 G, while the maximum positive value observed outside the Helmholtz coils was 22.6 G. The magnetic field strength was also found to be directly proportional to the strength of the electrical current running through the coils. Using the uniform magnetic field of the Helmholtz coils, the experimental e/m ratio of an electron was calculated to be 1.73x10 11 C/Kg with a standard deviation of 4.73x10 10 C/kg, which differed only by 1.64% from the accepted value of 1.7588 x 10 11 C/kg.
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Introduction and Theory Unlike electric fields which are generated by electric charges, magnetic fields have no magnetic charges. Every magnetic field has both a north and south pole, with the fields looping from the North to the South Pole indicating the orientation of the fields. When a magnet is broken it still maintains its North and South Pole on each piece. Scientifically, is has been impossible to isolate these fields but there are theories that predict that these isolated poles, monopoles, do actually exist. Magnetic fields, B, are measured in the unit Tesla, T, or gauss, G, which is equivalent to 10 -4 T. A compass consists of a magnetic needle that is free to rotate in the plane about its midpoint and when it is place in a magnetic field the north end of the needle will end up pointing toward the South Pole. The direction the needle points will in turn denote the direction of the magnetic field. Devices such as a solenoid or Helmholtz coil produce magnetic fields by moving electrical charges. The current flow from these devices cause magnetic field lines to form in a closed circle around the wire. To determine the direction of these magnetic field lines, a method called the right hand rule for electric currents can be used. The right hand rule states: 1) Point the thumb of your right hand in the direction of the current (I) in the wire (see
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This note was uploaded on 09/16/2008 for the course PHYS 1200 taught by Professor Bourdrou during the Spring '07 term at Pittsburgh.

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E/M Ratio - The e/m Ratio of the Electron Abstract In the...

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