Heating element

A heating element is a device used for conversion of electric energy into heat, consisting of a heating resistor and accessories. Heat is generated by the passage of electric current through a resistor through a process known as Joule heating. Heating elements are used in household appliances, industrial equipment, and scientific instruments enabling them to perform tasks such as cooking, warming, or maintaining specific temperatures higher than the ambient. Heating elements may be used to transfer heat via conduction, convection, or radiation. They are different from devices that generate heat from electrical energy via the Peltier effect, and have no dependence on the direction of electrical current.

A heating element is a device used for conversion of electric energy into heat, consisting of a heating resistor and accessories. Heat is generated by the passage of electric current through a resistor through a process known as Joule heating. Heating elements are used in household appliances, industrial equipment, and scientific instruments enabling them to perform tasks such as cooking, warming, or maintaining specific temperatures higher than the ambient. Heating elements may be used to transfer heat via conduction, convection, or radiation. They are different from devices that generate heat from electrical energy via the Peltier effect, and have no dependence on the direction of electrical current. Materials used in heating elements have a relatively high electrical resistivity, which is a measure of the material's ability to resist electric current. The electrical resistance that some amount of element material will have is defined by Pouillet's law as R = \rho \frac{\ell}{A} where R is the electrical resistance of a uniform specimen of the material \rho is the resistivity of the material \ell is the length of the specimen A is the cross-sectional area of the specimen The resistance per wire length (Ω/m) of a heating element material is defined in ASTM and DIN standards. In ASTM, wires greater than 0.127 mm in diameter are specified to be held within a tolerance of ±5% Ω/m and for thinner wires ±8% Ω/m. \Phi=P/A Power density is a measure of heat flux (denoted Φ) and is most often expressed in watts per square millimeter or watts per square inch. Heating elements with low power density tend to be more expensive but have longer life than heating elements with high power density. In the United States, power density is often referred to as 'watt density.' It is also sometimes referred to as 'wire surface load.' ===Metal alloys=== Resistance heating alloys are metals that can be used for electrical heating purposes above 600 °C in air. They can be distinguished from resistance alloys which are used primarily for resistors operating below 600 °C. While the majority of atoms in these alloys correspond to the ones listed in their name, they also consist of trace elements. Trace elements play an important role in resistance alloys, as they have a substantial influence on mechanical properties such as work-ability, form stability, and oxidation life. Some of these trace elements may be present in the basic raw materials, while others may be added deliberately to improve the performance of the material. The terms contaminates and enhancements are used to classify trace elements. Contaminates typically have undesirable effects such as decreased life and limited temperature range. Enhancements are intentionally added by the manufacturer and may provide improvements such as increased oxide layer adhesion, greater ability to hold shape, or longer life at higher temperatures. The most common alloys used in heating elements include: ==References==

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