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A cathode is the electrode at which electrons go into a cell, tube or diode whether driven externally or internally. It comes from the Greek word κάθοδος meaning, 'going down'. The other charged electrode in the same cell or device is the anode. Wikipedia does not have an article with this exact name. ...
Wikipedia does not have an article with this exact name. ...
General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ...
The Galvanic cell, named after Luigi Galvani, consists of two metals connected by an electrolyte which forms a salt bridge between the metals. ...
An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ...
Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ...
Diagram of a zinc anode in a Daniells cell. ...
Flow of electrons
The flow of electrons is always from anode–to–cathode outside of the cell or device and from cathode–to–anode inside the cell or device regardless of the cell or device type. Inside a chemical cell ions are carrying the electrons but the flow is still from cathode–to–anode inside the cell.
Chemistry cathode In chemistry a cathode is the electrode of an electrochemical cell at which reduction occurs (electrons are added to cations to complete the valence shell or bond). Chemistry (derived from the Arabic word kimia, alchemy, where al is Arabic for the) is the science that deals with the properties of organic and inorganic substances and their interactions with other organic and inorganic substances. ...
An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ...
An electrochemical cell is a setup used for creating an electromotive force(voltage) in a conductor separating two reactions. ...
The most fundamental reactions in chemistry are the redox processes. ...
Electrolytic cell In an electrolytic cell the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or pure metal from metal ions. Electrolytic cells are composed of an electrolyte (usually water or another solvent capable of dissolving various ions of interest), a cathode and an anode. ...
Galvanic cell In a galvanic cell the cathode is where the positive pole is connected to allow the circuit to be completed: as the anode of the galvanic cell gives off electrons they return from the circuit into the cell through the cathode. The Galvanic cell, named after Luigi Galvani, consists of two metals connected by an electrolyte which forms a salt bridge between the metals. ...
Electroplating metal cathode When metal ions are reduced from ionic solution onto the cathode they form a pure metal surface on the cathode. Items to be plated with pure metal are attached to and become part of the cathode in the electrolytic solution.
Electronics and physics cathode In physics or electronics a cathode is an electrode that emits electrons into the device. A black hole concept drawing by NASA. Physics (from the Greek, φυσικός (physikos), natural, and φÏσις (physis), nature) is the science of the natural world dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces. ...
Two digital voltmeters The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. ...
Vacuum tubes In a vacuum tube or other electronic vacuum system the cathode emits free electrons. Electrons are extracted from metal electrodes either by heating the electrode, causing thermionic emission, or by applying a strong electric field and causing field emission. Electrons can also be emitted from the electrodes of certain metals when light of frequency greater than the threshold frequency falls on it. This is called photoelectric emission. In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ...
Thermionic emission (archaically known as the Edison effect) is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ...
Also known as Fowler-Nordheim tunneling, field emission is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ...
An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ...
Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...
The photoelectric effect is the emission of electrons from a surface (usually metallic) upon exposure to, and absorption of, electromagnetic radiation (such as visible light and ultraviolet radiation) that is above the threshold frequency particular to each type of surface. ...
Cold cathodes and hot cathodes Cathodes used for field emission in vacuum tubes are called cold cathodes. Heated electrodes, frequently called filaments, are much more common. Most radios and television sets prior to the 1970s use filament heated cathode electron tubes for signal selection and processing as do many television sets to this day, forming the source of the electron beam in cathode ray tubes. Hot electron emitters are also are used as the electrodes in fluorescent lamps. Note: Principles are mostly the same for cold cathode ion sources as in particle accelerators to create electrons. ...
A filament is a fine, thinly spun thread, fiber, or wire. ...
The cathode ray tube or CRT, invented by Karl Ferdinand Braun, is the display device used in most computer displays, televisions and oscilloscopes. ...
A compact fluorescent lamp A fluorescent lamp is a type of electric lamp that excites argon and mercury vapor to create luminescence. ...
Diodes In a semiconductor diode the cathode is the N–doped layer of the NP junction. Initially the N-doped layer supplies 'holes' to flow into the junction. The holes given by the N-doped layer combine with electrons supplied from the P-doped layer. The electrons and holes combining creates a 'depleted' zone at the junction leaving behind a layer in the cathode of negative ions which gives a base negative charge to the cathode side of device (N-doped for negative charge carrier ions). (The anode side has a base positive charge this point since it supplied electrons to the recombinant region and the doped ions are short of a full valence shell of electrons). As a negative charge is applied to the cathode from the circuit external to the diode more N-doped ions are able to supply 'holes' to the recombinant region and the diode becomes conductive which allows electrons to flow though the diode from the cathode to the anode (electrons flow from N-doped to P-doped when the bias is overcome). Unlike a typical diode, there is no fixed anode or cathode in a zener diode. Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. ...
Types of diodes In electronics, a diode is a component that restricts the direction of movement of charge carriers. ...
Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...
Diagram of a zinc anode in a Daniells cell. ...
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