Cathode ray tube
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The cathode ray tube or CRT, invented by Karl Ferdinand Braun, is the display device that was traditionally used in most computer monitors, televisions, radar displays and oscilloscopes.
A cathode ray tube can be described as none other than an electron gun. It is a vacuumed glass container with a cathode (a negative electrode) at one end. Then there is an electron gun that fires a beam of electrons onto a luminescent screen. Where ever the screen turns bright that is where the electrons are hitting.
The way a CRT works is that electrons are created from a heated cathode and then shot into the electron gun. Next a series of grids that have positive potential, accelerate the electrons as they pass. The next stage the electron goes through the gun, during this process it passes through a series of doughnut shaped anodes, that focus the electrons so when it hits the screen it hits on a fine point.
Between the gun and the screen there are two sets of either electric deflecting plates or two magnetic deflecting coils. The difference is that electric deflecting plates are used in smaller CRTs, while magnetic deflecting plates are used in large CRTs. In the CRT that uses electric deflecting plates it works, by a set of horizontal plates controlling the up and down motion of the beam. And a vertical pair controlling the left and right motion of the beam. In each plate there is a set charge being one of them has a positive charge while the other has a negative charge. If the charges are equal in value then the beam will hit in the center of the screen but if the charges are unequal the beam will move into other areas of the screen depending on the difference of charge. Magnetic deflecting coils work in the same manner except for the electron beam is deflected by the different strengths in the magnets.
