Xerox copier and oscilloscope.
In the electrostatic copier, the document is lighted and its image is projected onto a Sellenium cylinder.
The dark parts will be charged and atract the tonner powder, wich will be transferred to a blank sheet of paper and melted to be fixed on it. That's why the copies are warm when they leave the machine.
In the oscilloscope, the electron bean will be deflected up and down or left/right depending on the potential at the deflection plates. It is similar to a Cathode Ray Tube (used in old TVs and computer monitors). The difference is that in the CRT the deflection is electromagnetic, instead of electrostatic.