In this simulation an electron beam is launched in a region where there is a magnetic field (the electron launch speed is always perpendicular to the magnetic field). The trajectory of the electrons can be visualized by a blue line. The speed of electrons can be varied by changing the acceleration potential (V). The magnetic field perpendicular to the plane of the figure can be varied within pre-established limits. A ruler makes it possible to measure the diameter of the trajectory of the particles. The simulation allows you to calculate the charge-to-mass ratio of the electron. ATTENTION: This simulation was developed (deliberately) in order to provide the Charge/Mass Ratio with a small experimental error, just as it would occur in a real experiment.