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Unformatted text preview: Physics Lab Lab 3 e/m of the electron Aleksey Zelenberg Introduction This experiment indirectly measured the charge to mass ratio of an electron (e/m), one of the basic physical constants in nature along with the magnetic field of the earth. Our results indicate an e/m ratio of 1.91108*10 11 .00161*10 11 C/kg. For the preliminary part of the experiment, we obtained a B E value of 3.92*10-5 1.96*10-5 T. For the main part of the experiment, we obtained a B E value of 1.416*10-5 0.513*10-6 T. The value we obtained for e/m is on the correct order of magnitude with the accepted value of 1.758*10 11 C/kg. However, even within the statistical error range, this accepted value does not correspond to our obtained ratio. Our value of B E , both from preliminary part of the experiment, and the value obtained from graphical intercepts, also does not correspond with the accepted value of 5*10-5 T. Procedure The procedure in this experiment is fairly straightforward. There is a direct correlation between the current in the Helmholtz coils and the inverse of the radius of curvature given by the following equation: By taking measurements of the various currents needed to produce given radii at particular voltages, it is possible to determine both e/m and B E with graphical methods. After noting the dip angle (an angle that is used to find the true value of the earths magnetic field), we obtained a preliminary measurement of B E...
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