electrode n : a conductor used to make electrical contact with some part of a circuit
the terminal through which electric current passes
- Spanish: electrodo
An electrode is an electrical conductor used to make 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.
Anode and cathode in electrochemical 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 voltage applied to the cell. A bipolar electrode is an electrode that functions as the anode of one cell and the cathode of another cell.
Primary cellA 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.
Secondary cellA secondary cell, for example a rechargeable battery, is one in which the reaction is reversible. When the cell is being charged, the anode becomes the positive (+) electrode and the cathode the negative (−). This is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a primary or voltaic cell, with the anode as the negative electrode and the cathode as the positive. The chemical change, which converts chemical energy into electrical energy, is reversible. This cell can be recharged by simply passing electrons in the opposite direction, so it is also called a storage or accumulator cell.
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 electrons enter the device through the cathode and exit the device through the anode.
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.
Welding electrodesIn arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. Depending 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.
Alternating current electrodesFor electrical systems which use alternating current the electrodes are the connections from the circuitry to the object to be acted upon by the electrical current but are not designated anode or cathode since the direction of flow of the electrons changes periodically, usually many times per second.
Uses of electrodesElectric currents are run through nonmetal objects to alter them in numerous ways and to measure conductivity for numerous purposes. Examples include:
- Electrodes for medical purposes, such as EEG, ECG, ECT, defibrillator
- Electrodes for electrophysiology techniques in biomedical 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 using electrochemical methods
- Inert electrodes for electrolysis (made of platinum)
electrode in Azerbaijani: Elektrod
electrode in Bosnian: Elektroda
electrode in Catalan: Elèctrode
electrode in Czech: Elektroda
electrode in Danish: Elektrode
electrode in German: Elektrode
electrode in Spanish: Electrodo
electrode in French: Électrode
electrode in Ido: Elektrodo
electrode in Indonesian: Elektroda
electrode in Italian: Elettrodo
electrode in Hebrew: אלקטרודה
electrode in Latvian: Elektrods
electrode in Dutch: Elektrode
electrode in Japanese: 電極
electrode in Norwegian: Elektrode
electrode in Novial: Elektrode
electrode in Polish: Elektroda
electrode in Portuguese: Eletrodo
electrode in Slovak: Elektróda
electrode in Simple English: Electrode
electrode in Finnish: Elektrodi
electrode in Swedish: Elektrod
electrode in Turkish: Elektrot
electrode in Ukrainian: Електрод
electrode in Chinese: 电极