electron beam. A thin stream of electrons all moving in the same direction under the influence of electrical or magnetic fields. Electron beams may be focused and directed by these fields.
When an electron beam strikes certain phosphors, electroluminescence is produced and the phosphor glows. This is the way the image is formed on a television screen and on the face of a cathode-ray tube.
electron-beam welding. A method of welding metal by the heat produced when a high-speed stream of electrons strikes the metal. Electron-beam welding is used in applications in which the heat must be concentrated at the point the weld is being made.
electron current. The movement of electrons through a circuit from the negative terminal of the power source to its positive terminal.
Electron current moves in the direction opposite the direction of the arrowheads in the symbol for a semiconductor diode. These symbols are drawn to follow conventional current, an imaginary flow considered to be from positive to negative. Electron current is the actual movement of electrons.
electron drift. The relatively slow movement of individual electrons through a conductor. Electron drift is not the same as electron flow, or electron current.
electronic. Relating to the application of the flow of free electrons through semiconductor devices and across a vacuum.
electronic emission. The discharge of electrons from a material. Electrons are held tightly in their atoms, but certain kinds of outside energy can cause them to move from one atom to another.
When heat energy causes electrons to leave, the emission is called thermal emission. When the electrons are moved out of their atoms by light energy, the emission is called photoemission.
electronic leak detector (air conditioning system servicing tool). An electronic oscillator whose frequency changes if refrigerant gas is picked up in its sensor tube. The sensor tube is held below a suspected leak, and if any refrigerant is leaking, the sound produced by the oscillator will change from a low tone to a high-pitched squeal. Electronic leak detectors can detect a leak as small as a few parts of refrigerant gas in a million parts of air.
electronic oscillator. An electronic circuit that converts DC electricity into AC electricity.
electronics. The study and use of the movement of free electrons. In electricity, we normally think of the movement of electrons only through conductors; but in electronics, we also consider the movement of electrons through materials that are not always conductors. Electrons can be caused to flow through a vacuum and through semiconductor materials such as silicon and germanium.
electronic voltmeter. A special type of electronic instrument used to measure voltage. Electronic voltmeters use electron tubes or solid-state components, such as field-effect transistors (FET), to amplify the voltage being measured before it is read by the indicating instrument.
An electronic voltmeter has a much higher input impedance than a nonelectronic meter, and it can measure AC voltages having a wider range of frequencies.
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