Everything about Electrode totally explained
An
electrode is an
electrical conductor used to make contact with a nonmetallic part of a
circuit (for example 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 cell
A
primary cell is a special type of electrochemical cell in which the reaction can't 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 cell
A
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's also called a storage or accumulator cell.
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 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 electrodes
In
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 wouldn't be considered an anode or cathode.
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 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 electrodes
Electric currents are run through nonmetal objects to alter them in numerous ways and to measure conductivity for numerous purposes. Examples include:
Further Information
Get more info on 'Electrode'.
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