magnetic field is produced at the midway point. The currents in the coils must yield fields of the coils that are in the same direction as their common axis. At a central point, the magnitude of the flux density B is: N is the number of turns per coil. In this experiment N=129. I is the current in the coils. This is always changing. R is the coil radius. For the experiment R=10.75 is the permeablilty of free space. =4 *10^-7 weber/amp*m . Later we will come to find that when the specified units are used, e/m is expressed in coulombs/kilogram.Data: Connect the apparatus as shown in the following diagram. The electron stream should have a diameter of about 2mm. Set the rheostat for high resistance close to the circuit field coils and then vary the current to (3-5) amp until the electron beam bends into a complete semicircle. Arrange the plate potential so that the accelerating potential difference can very and change the field current until the beam falls on the marked circles. The plate potential, the field current, and the radius of the described circle were recorded as follows. Because these values for e/m were so different than the predicted value of e/m (1.75890*10^11 coulombs/kg) the experiment was run a second time, but with a higher voltage and current. The data was recorded as follows:Conclusion: From this data, and use of the working equation for e/m, it can be concluded that our experiment was consistent, but off from the given value of e/m by a fairly constant amount. This can be caused by several sources of error. One might be that we did not take the magnetic field of the earth into account. Another could be a magnetic field created by a nearby object. Still a third source of error might have been that we could not determine which ring on the plate that the electron beam curve actually hit. This experiment does show that given a Magnetic field, a V, an I, and an R, we can calculate e/m and compare t...
