A vertically oriented vacuum tube containing a trace of inert gas contains an electrode assembly oriented to emit a focused beam of electrons horizontally, creating a visible fine beam. The tube and base can be rotated about their vertical axis, varying the orientation of the electron beam to a pair of Helmholtz coils. This allows magnetic deflection of the beam to be demonstrated. Circular, helical, or undeflected paths can be seen. Built-in LED indicators show the direction of current flow in the Helmholtz coils and allow students to use the Lorentz relation to show that the electronic charge is negative. A pair of electrode plates is attached to the main electrode assembly to demonstrate electrostatic deflection. To measure e/m, the electron beam is accelerated at a known voltage and deflected into a circular path by a known coil current. Using a detachable scale that fits in front of the tube, the circle's diameter can be measured, giving enough data to calculate e/m. The compact base of the unit contains a power supply that provides all the required potentials, and has built-in panel meters for the coil current and beam accelerating voltage. The entire apparatus is contained in a wooden case for better visibility of the beam and convenient storage. Operates on 110V/60Hz AC. Manual included.