A typical television picture tube (the technology on which I watched TV as a child) may accelerate electrons horizontally with a potential difference of about 25,000 Volts. The moving electrons are then given a vertical velocity component by electric or magnetic fields in a region we will assume to be 10 cm long. When the electrons leave the accelerating region they then travel a horizontal distance of 40 cm and strike a glass surface. See the figure below. Glass Surface -25,000v 0v Deflection _____ Vertical Region Deflection -------------------------------- ..--:::I'. ............................................................... l , B or E Field electrons