Portions of this entry contributed by Leonardo Motta

The simplest version of a cathode ray tube consists of a gas-filled glass tube in which two metal plates, one negatively charged (the cathode) and the other positively charged (the anode), have been placed. When a very large voltage is placed across the electrodes, the neutral gas inside the tube will ionize into a conducting plasma, and a current will flow as electrons travel from the cathode to the other side.

The cathode ray tube was used in the experiments of Röntgen and J. J. Thomson that led to the discoveries of X-rays and the electron, respectively. Cathode ray tubes remain familiar objects today as a result of the popularity of the neon sign.

In electrical engineering, the term "cathode ray tube" (abbreviated CRT in this context) is also used to refer to a tube containing a cathode and a luminescent screen. Each time an electron from the cathode hits the screen, a spot of light appears, and this is the technology used on conventional television sets and computer monitors.

Anode, Cathode, Plasma, Vacuum Tube