Electrode
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Electrode For other uses, see Electrode (disambiguation). An electrode is an electrical conductor used to make Electrodes used in arc welding contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte or a vacuum). The word was coined by the scientist Michael Faraday from the Greek words elektron (meaning amber, from which the word electricity is derived) and hodos, a way. [1] 1 Anode and cathode in electro- chemical cells An electrode in an electrochemical cell is referred to as either an anode or a cathode (words that were also coined by Faraday). The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs, and the cathode as the electrode at which electrons enter the cell and reduction occurs. Each electrode may become either the anode or the cathode depending on the direc- tion of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell and the cathode of another cell. 1.1 Primary cell A primary cell is a special type of electrochemical cell in which the reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode. The cell can be discharged but not recharged. 1.2 Secondary cell A secondary cell, for example a rechargeable battery, is a cell in which the chemical reactions are reversible. When the cell is being charged, the anode becomes the positive (+) and the cathode the negative (−) electrode. This is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a primary cell, with the anode as the negative and the cathode as the positive electrode. 2 Other anodes and cathodes In a vacuum tube or a semiconductor having polarity (diodes, electrolytic capacitors) the anode is the positive (+) electrode and the cathode the negative (−). The elec- trons enter the device through the cathode and exit the device through the anode. Many devices have other elec- trodes to control operation, e.g., base, gate, control grid. In a three-electrode cell, a counter electrode, also called an auxiliary electrode, is used only to make a connection to the electrolyte so that a current can be applied to the working electrode. The counter electrode is usually made of an inert material, such as a noble metal or graphite, to keep it from dissolving. 3 Welding electrodes In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. Depend- ing upon the process, the electrode is either consumable, in the case of gas metal arc welding or shielded metal arc welding, or non-consumable, such as in gas tungsten arc welding. For a direct current system the weld rod or stick may be a cathode for a filling type weld or an anode for other welding processes. For an alternating current arc welder the welding electrode would not be considered an anode or cathode. 4 Alternating current electrodes For electrical systems which use alternating current the electrodes are the connections from the circuitry to the object to be acted upon by the electric current but are not designated anode or cathode because the direction of flow 1
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ELECTRODE
Transcript of Electrode
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Electrode
For other uses, see Electrode (disambiguation).An electrode is an electrical conductor used to make
Electrodes used in arc welding
contact with a nonmetallic part of a circuit (e.g. asemiconductor, an electrolyte or a vacuum). The wordwas coined by the scientist Michael Faraday from theGreek words elektron (meaning amber, from which theword electricity is derived) and hodos, a way.[1]
1 Anode and cathode in electro-chemical cells
An electrode in an electrochemical cell is referred to aseither an anode or a cathode (words that were also coinedby Faraday). The anode is now dened as the electrode atwhich electrons leave the cell and oxidation occurs, andthe cathode as the electrode at which electrons enter thecell and reduction occurs. Each electrode may becomeeither the anode or the cathode depending on the direc-tion of current through the cell. A bipolar electrode is anelectrode that functions as the anode of one cell and thecathode of another cell.
1.1 Primary cell
A primary cell is a special type of electrochemical cell inwhich the reaction cannot be reversed, and the identitiesof the anode and cathode are therefore xed. The anode isalways the negative electrode. The cell can be dischargedbut not recharged.
1.2 Secondary cell
A secondary cell, for example a rechargeable battery, is acell in which the chemical reactions are reversible. Whenthe cell is being charged, the anode becomes the positive(+) and the cathode the negative () electrode. This isalso the case in an electrolytic cell. When the cell is beingdischarged, it behaves like a primary cell, with the anodeas the negative and the cathode as the positive electrode.
2 Other anodes and cathodesIn a vacuum tube or a semiconductor having polarity(diodes, electrolytic capacitors) the anode is the positive(+) electrode and the cathode the negative (). The elec-trons enter the device through the cathode and exit thedevice through the anode. Many devices have other elec-trodes to control operation, e.g., base, gate, control grid.In a three-electrode cell, a counter electrode, also calledan auxiliary electrode, is used only to make a connectionto the electrolyte so that a current can be applied to theworking electrode. The counter electrode is usually madeof an inert material, such as a noble metal or graphite, tokeep it from dissolving.
3 Welding electrodesIn arc welding an electrode is used to conduct currentthrough a workpiece to fuse two pieces together. Depend-ing upon the process, the electrode is either consumable,in the case of gas metal arc welding or shielded metal arcwelding, or non-consumable, such as in gas tungsten arcwelding. For a direct current system the weld rod or stickmay be a cathode for a lling type weld or an anode forother welding processes. For an alternating current arcwelder the welding electrode would not be considered ananode or cathode.
4 Alternating current electrodesFor electrical systems which use alternating current theelectrodes are the connections from the circuitry to theobject to be acted upon by the electric current but are notdesignated anode or cathode because the direction of ow
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2 8 REFERENCES
of the electrons changes periodically, usually many timesper second.
5 UsesElectrodes are used to provide current through nonmetalobjects to alter them in numerous ways and to measureconductivity for numerous purposes. Examples include:
Electrodes for fuel cells Electrodes for medical purposes, such as EEG,ECG, ECT, debrillator
Electrodes for electrophysiology techniques inbiomedical research
Electrodes for execution by the electric chair Electrodes for electroplating Electrodes for arc welding Electrodes for cathodic protection Electrodes for grounding Electrodes for chemical analysis usingelectrochemical methods
Inert electrodes for electrolysis (made of platinum) Membrane electrode assembly
6 Chemically modied electrodesChemically modied electrodes are electrodes that havetheir surfaces chemically modied to change the elec-trodes physical, chemical, electrochemical, optical,electrical, and transport properties. These elec-trodes are used for advanced purposes in research andinvestigation.[2]
7 See also Working electrode Reference electrode Gas diusion electrode Battery Redox Reaction Cathodic protection Galvanic cell Anion vs. Cation
Electron versus hole Electrolyte Electron microscope Noryl Tafel equation Hot cathode Cold cathode Electrolysis
8 References[1] Faraday, Michael (1834). On Electrical Decomposi-
tion. Philosophical Transactions of the Royal Soci-ety. Archived from the original on 2010-01-17. Re-trieved 2010-01-17. ( (in which Faraday coins thewords electrode, anode, cathode, anion, cation, electrolyte,electrolyze)
[2] Durst, R., Baumner, A., Murray, R., Buck, R., & An-drieux, C., "Chemically modied electrodes: Recom-mended terminology and denitions (PDF)", IUPAC,1997, pp 13171323.
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39 Text and image sources, contributors, and licenses9.1 Text
Electrode Source: http://en.wikipedia.org/wiki/Electrode?oldid=636536590 Contributors: The Anome, Tarquin, Heron, JohnOwens,Ixfd64, Prefect, Minesweeper, Mac, Theresa knott, Kingturtle, Andrewa, Glenn, Andres, Rob Hooft, Lommer, The Anomebot, Zoicon5,Omegatron, Jerzy, Donarreiskoer, Gentgeen, Robbot, Naddy, Hadal, Giftlite, Mintleaf, AJim, Christopherlin, OldakQuill, Antandrus,Sparky the Seventh Chaos, Andros 1337, El C, Femto, Jpgordon, Bobo192, Kjkolb, Hagerman, Hooperbloob, JYolkowski, Arthena, Riana,Sade, Spangineer, Snowolf, Jonathan888, King Bowser 64, Computerjoe, Snowmanmelting, Pol098, Cbdorsett, Graham87, Canderson7,Astronaut, NeonMerlin, User142, Margosbot, Crazycomputers, Gurch, Chobot, YurikBot, NTBot, Kafziel, Postglock, Salsb, RadioKirk,NawlinWiki, Kyle Barbour, Bota47, Cinik, Wknight94, 21655, Itub, TravisTX, Cafe Nervosa, Reedy, Jrockley, BiT, Edgar181, Jwest-brook, Bluebot, Kurykh, Viperphantom, Pax85, Mion, Ph89, Tucuxi, Daniel5127, Ilikefood, JohnCD, Christian75, Escarbot, AntiVan-dalBot, Seaphoto, Squantmuts, Res2216restar, MER-C, .anacondabot, VoABot II, Philg88, InvertRect, Koska98, EyeSerene, Anaxial,Glrx, R'n'B, CommonsDelinker, Leyo, Yonidebot, Dbiel, L'Aquatique, AntiSpamBot, JavierMC, Jalan107, MichelJullian, Funandtrvl,VolkovBot, Clancy60, TXiKiBoT, Gwib, HansMair, Bamelement199, SieBot, Tiptoety, Faradayplank, MEDISTIM, ClueBot, Frmorri-son, Jonbowers, Alexbot, Noraneko, Ark25, Kcnt, Nielsbogerd, WikiDao, Crazysane, Tide rolls, Lightbot, EugeneZ, Legobot, Luckas-bot,Yobot, Harkain, Daniele Pugliesi, Carlsotr, ArthurBot, AbigailAbernathy, , SassoBot, Mnmngb, Rainald62, SD5, Laaa200,Pinethicket, TobeBot, , Stegop, EmausBot, John of Reading, Ajraddatz, Dcirovic, Hhhippo, 15turnsm, WRONG -EDIT-MAN, Gz33, Swan8706, Carmichael, Stanstanstanstanstan, ClueBot NG, Lforscht, GoldenGlory84, Braincricket, Mmarre, Yeldho7,Aathisemithran.d, Vanischenu, Cimorcus, Mayadyad, Shyamcalm, CFA213FCE, Mohit rajpal, Omegaweld, Beckx385, Quarter2002 andAnonymous: 170
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Anode and cathode in electrochemical cells Primary cell Secondary cell
Other anodes and cathodes Welding electrodes Alternating current electrodes Uses Chemically modified electrodesSee also References Text and image sources, contributors, and licensesTextImagesContent license
