Assembling a Velocity Filter (Wien Filter) to Determine the Specific Electron Charge
In the experiment P3.8.5.2, a velocity filter (Wien filter) is constructed using crossed electrical and magnetic fields. Among other things, this configuration permits a more precise determination of the specific electron charge. At a fixed anode voltage UA, the current I of the Helmholtz coils and the deflection voltage UP are set so that the effects of the electric field and the magnetic field just compensate each other. The path of the beam is then virtually linear, and we can say: