Conduction: Difference between revisions
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[[File:copper-wire-113249_640_resized.jpg|frame|right|Figure 1. Common metals, such as copper, display both thermal and electrical conductivity <ref> Pixabay. (2013). ''Copper-wire'' [Online]. Available: http://pixabay.com/p-113249/?no_redirect. </ref>]] | [[Category:Translated to French]] | ||
[[fr:Conduction]] | |||
[[File:copper-wire-113249_640_resized.jpg|frame|right|Figure 1. Common metals, such as copper, display both thermal and electrical conductivity.<ref> Pixabay. (2013). ''Copper-wire'' [Online]. Available: http://pixabay.com/p-113249/?no_redirect. </ref>]] | |||
<onlyinclude>'''Conduction''' can refer to either: | <onlyinclude>'''Conduction''' can refer to either: | ||
*[[Thermal conduction]]: the physical property of [[heat]] moving through material<ref name=thermal> Boston University. (1998). ''Heat Transfer, and The First Law of Thermodynamic'' [Online]. Available: http://physics.bu.edu/~duffy/py105/notes/Heattransfer.html</ref> | *[[Thermal conduction]]: the physical property of [[heat]] moving through material<ref name=thermal> Boston University. (1998). ''Heat Transfer, and The First Law of Thermodynamic'' [Online]. Available: http://physics.bu.edu/~duffy/py105/notes/Heattransfer.html</ref> | ||
*[[Electrical conduction]]: the physical property of [[electricity]] moving through material</onlyinclude><ref name = virg> Virginia Universiy. ''Electrical Conduction'' [Online]. Available: http://www.virginia.edu/bohr/mse209/chapter19.htm</ref> | *[[Electrical conduction]]: the physical property of [[electricity]] moving through material</onlyinclude><ref name = virg> Virginia Universiy. ''Electrical Conduction'' [Online]. Available: http://www.virginia.edu/bohr/mse209/chapter19.htm</ref> | ||
The word [[conductor]] usually means a material with high [[electrical conductivity]] (low [[resistivity]]). However, most electric conductors (usually [[metal]]s), are good thermal conductors as well.<ref name = ecooling> Electronics Cooling. (2000). ''How Thermal Conductivity Relates to Electrical Conductivity'' [Online]. Available: http://www.electronics-cooling.com/2000/05/how-thermal-conductivity-relates-to-electrical-conductivity/</ref> For example, [[copper]] is both an excellent thermal conductor and electrical conductor. | The word [[conductor]] usually means a material with high [[electrical conductivity]] (low [[resistivity]]). However, most electric conductors (usually [[metal]]s), are good thermal conductors as well.<ref name = ecooling> Electronics Cooling. (2000). ''How Thermal Conductivity Relates to Electrical Conductivity'' [Online]. Available: http://www.electronics-cooling.com/2000/05/how-thermal-conductivity-relates-to-electrical-conductivity/</ref> For example, [[copper]] is both an excellent thermal conductor and electrical conductor. A simple [[model]] that explains this relationship (a good conceptual model, but it skips some important details) is pretending that the electrons in the metal behave like a gas that are free to move and carry both electric current and heat. | ||
==Ratio of Thermal to Electrical Conductivity== | |||
The values for thermal conductivity and electrical conductivity for many metals depend on temperature. The higher the temperature the greater the thermal conduction (compared to electrical conduction). This linear relationship can be expressed and compared using a ratio known as the '''Wiedemann-Franz law'''. This ratio is expressed as:<ref name=hp>HyperPhysics. (May 12, 2015). ''Thermal Conductivity'' [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html</ref> | |||
<center><big><math> \frac{\kappa}{\sigma}= LT = \frac{\pi^2 k^2}{3 e^2} T = 2.45\times 10^{-8} \frac{\textrm{W}\Omega}{\textrm{K}^2} T </math></big></center> | |||
Where: | |||
* <math>L</math> is a constant known as the ''Lorentz number'', equal to <math>2.45\times 10^{-8} \frac{\textrm{W}\Omega}{\textrm{K}^2}</math> | |||
* <math>\kappa</math> is the thermal conductivity of the material | |||
* <math>\sigma</math> is the [[electrical conductivity]] of the material | |||
* <math>T</math> is the temperature of the material, in Kelvin | |||
* <math>k</math> is the [[Boltzmann's constant]] | |||
* <math>e</math> is the elementary charge of an [[electron]] | |||
The reverse is usually but not always true;<ref name=ecooling /> for example, diamonds are excellent thermal conductors (even better than copper) but usually [[electrical insulator]]s. Although at very low temperatures a research group found <ref>Ekimov et al., "Superconductivity in diamond" in ''Nature'', Vol. 428, New York: MacMillan, 2004, pp. 542-5. Available: http://www.nims.go.jp/NFM/paper1/SuperconductingDiamond/01nature02449.pdf</ref> showing that diamonds can become [[superconductor]]s below 4 [[Kelvin|K]] (superconductivity is specifically a description of electrical conduction, not thermal conduction). | The reverse is usually but not always true;<ref name=ecooling /> for example, diamonds are excellent thermal conductors (even better than copper) but usually [[electrical insulator]]s. Although at very low temperatures a research group found <ref>Ekimov et al., "Superconductivity in diamond" in ''Nature'', Vol. 428, New York: MacMillan, 2004, pp. 542-5. Available: http://www.nims.go.jp/NFM/paper1/SuperconductingDiamond/01nature02449.pdf</ref> showing that diamonds can become [[superconductor]]s below 4 [[Kelvin|K]] (superconductivity is specifically a description of electrical conduction, not thermal conduction). | ||
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*[[Electrical conduction]] | *[[Electrical conduction]] | ||
*[[Conductor]] | *[[Conductor]] | ||
*[[ | *[[R-value]] | ||
*[[ | *[[Fibrous insulation]] | ||
*Or explore a [[Special:Random|random page]] | *Or explore a [[Special:Random|random page]] | ||
Latest revision as of 00:03, 27 September 2021
Figure 1. Common metals, such as copper, display both thermal and electrical conductivity.[1]
Conduction can refer to either:
- Thermal conduction: the physical property of heat moving through material[2]
- Electrical conduction: the physical property of electricity moving through material[3]
The word conductor usually means a material with high electrical conductivity (low resistivity). However, most electric conductors (usually metals), are good thermal conductors as well.[4] For example, copper is both an excellent thermal conductor and electrical conductor. A simple model that explains this relationship (a good conceptual model, but it skips some important details) is pretending that the electrons in the metal behave like a gas that are free to move and carry both electric current and heat.
Ratio of Thermal to Electrical Conductivity
The values for thermal conductivity and electrical conductivity for many metals depend on temperature. The higher the temperature the greater the thermal conduction (compared to electrical conduction). This linear relationship can be expressed and compared using a ratio known as the Wiedemann-Franz law. This ratio is expressed as:[5]
Where:
- is a constant known as the Lorentz number, equal to
- is the thermal conductivity of the material
- is the electrical conductivity of the material
- is the temperature of the material, in Kelvin
- is the Boltzmann's constant
- is the elementary charge of an electron
The reverse is usually but not always true;[4] for example, diamonds are excellent thermal conductors (even better than copper) but usually electrical insulators. Although at very low temperatures a research group found [6] showing that diamonds can become superconductors below 4 K (superconductivity is specifically a description of electrical conduction, not thermal conduction).
For Further Reading
- Thermal conduction
- Electrical conduction
- Conductor
- R-value
- Fibrous insulation
- Or explore a random page
References
- ↑ Pixabay. (2013). Copper-wire [Online]. Available: http://pixabay.com/p-113249/?no_redirect.
- ↑ Boston University. (1998). Heat Transfer, and The First Law of Thermodynamic [Online]. Available: http://physics.bu.edu/~duffy/py105/notes/Heattransfer.html
- ↑ Virginia Universiy. Electrical Conduction [Online]. Available: http://www.virginia.edu/bohr/mse209/chapter19.htm
- ↑ 4.0 4.1 Electronics Cooling. (2000). How Thermal Conductivity Relates to Electrical Conductivity [Online]. Available: http://www.electronics-cooling.com/2000/05/how-thermal-conductivity-relates-to-electrical-conductivity/
- ↑ HyperPhysics. (May 12, 2015). Thermal Conductivity [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html
- ↑ Ekimov et al., "Superconductivity in diamond" in Nature, Vol. 428, New York: MacMillan, 2004, pp. 542-5. Available: http://www.nims.go.jp/NFM/paper1/SuperconductingDiamond/01nature02449.pdf