This lesson discusses the result of a charge being subject to both electric and magnetic fields at the same time. It covers the Hall effect, velocity selector, and the charge to mass ratio. Given several sample problems, learners learn to calculate the Hall Voltage dependent upon the width of the plate, the drift velocity, and the strength of the magnetic field. Then students learn to calculate the velocity selector, represented by the ratio of the magnitude of the fields assuming the strength of each field is known. Finally, learners proceed through a series of calculations to arrive at the charge to mass ratio. A homework set is included as an evaluation of student progress.