In this lab, you can explore the three phases in a mass spectrometer.

In the acceleration phase, a particle with a positive charge is released from rest near the positive plate of a parallel-plate capacitor. The particle accelerates across the gap and comes out a hole in the negative plate. Adjust the electric field to see how that affects the particle.

In the velocity selector, there is both a downward directed electric field and a magnetic field directed into the page. The electric field applies a downward force to the particle, and the magnetic field applies a force that is initially upward. Adjust the speed of the particle and observe how the path the particle follows is affected.

Only particles that pass undeflected through the velocity selector enter the mass separator, which is simply a region with a uniform magnetic field directed out of the page. The radius of the path followed by a particle is proportional to the mass of the particle, so particles are separated by mass.