Physics307L F08:People/Knockel/Lab2

Electron's e/m ratio summary
The e/m ratio (charge to mass ratio) for an electron can, in theory, be measured by seeing how an electron beam behaves in a magnetic field. Using a Helmholtz coil to generate the field and an electron gun in a vacuum tube filled with helium, a beam can be created, formed into a circle with the magnetic field, and measured (since the electrons makes the helium glow).

This experiment was a disaster since there was ridiculous drag from the helium and for other reasons. The only thing I could conclude was that

$$\frac{e}{m} < 3.13\times10^{11}\frac{C}{kg}$$.

Taking e/m = 3.13x1011 C/kg, there is a relative error of 78% from the actual value of 1.76x1011 C/kg.

In my lab notebook, I go into great detail explaining the theory, why there is so much systematic error, and alternative methods for finding e/m without so much error. I, of course, also explain the setup, equipment, procedure, etc., and I give my data and calculations.

link to e/m ratio notebook