Teltron Tube. This is an experimental apparatus used to demonstrate the motion of electrically charged particles in a uniform electric field. The electrons are accelerated from the component at right into a uniform electric field between two parallel plates. These have a large potential difference between them, here four kilovolts between the top and bottom plates, with the top plate positively charged relative to the bottom plate. Electrons have a negative charge, and therefore accelerate towards the positive plate (upwards), as seen by the blue track. The force on the electrons is directed vertically, and there is no component of force in the horizontal direction. The result is that the electrons follow a parabolic path toward the positively charged plate. See clip K004/1377 for an animation showing this.