Cathode Ray Tube

A cathode ray tube (CRT) creates an electron beam that is displayed as a dot on a screen. The electron beam (and thus the dot) can be moved with a power supply, which creates a potential difference to alter the path of the beam in a direction that depends on its polarity (demonstrated in the first video). The beam can also be deflected with a magnet, which alters the path of the beam depending on its polarity (demonstrated in the second video).