Velocity selector for charged particles
The velocity selector is a mechanism for filtering charged particles by velocity, enabled by the Lorentz force law. The setup involves crossed fields, that is an Electric field running perpendicular to the magnetic one. Particles of varied velocity are fired perpendicular to both of these fields, and as such experience two deflecting forces: an electric force in one direction and a magnetic Lorentz force in the other. At a specific speed determined by the respective strength of these fields, these two forces are equal and cancel out, whereby the particle passes through undeflected.