Conductivity: Difference between revisions
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'''Maxwell's Equation for Electric Conductivity''''''--[[User:Rwilliams354|Rwilliams354]] ([[User talk:Rwilliams354|talk]]) 14:13, 27 November 2016 (EST) | '''Maxwell's Equation for Electric Conductivity''''''--[[User:Rwilliams354|Rwilliams354]] ([[User talk:Rwilliams354|talk]]) 14:13, 27 November 2016 (EST) | ||
J=(conductivity)E--[[User:Rwilliams354|Rwilliams354]] ([[User talk:Rwilliams354|talk]]) 14:13, 27 November 2016 (EST) | J=(conductivity)E --[[User:Rwilliams354|Rwilliams354]] ([[User talk:Rwilliams354|talk]]) 14:13, 27 November 2016 (EST) | ||
J= Electric Current Density | J= Electric Current Density |
Revision as of 14:56, 27 November 2016
Claimed by myoung65, Spring 2016
Claimed by Reed Williams Fall 2016
Definition
Electrical Resistivity is a measure of how a given material opposes current flow. Low resistivity shows a material that allows the flow of current, whereas the opposite is true for high resistivity. Electrical Conductivity is the reciprocal/inverse of Electrical Resistivity, in that it measures the ability of a given material to conduct electric current
Symbols
Electrical Resistivity is mainly represented by the Greek lower-case rho. Electrical Conductivity is mainly represented by the Greek lower-case sigma, but is occasionally represented by a lower-case kappa, or gamma.
SI Units
Electrical Resistivity is measured in Ohm-Metres. Electrical Conductivity is measured in Siemens per Metre
Classification of Materials by Conductivity
Conductors, Semiconductors, and Insulators are the main three classifications of a material when talking about its electrical conductivity. Conductors are materials with high conductivity. Semiconductors have an in between level of conductivity, while insulators have low conductivity. Meaning if you want to pass a lot of electricity to something use a conductor, if you want to pass some electricity but also lower the original amount use a semiconductor, and if you want to cut the flow of electricity use an insulator. Provided below is a list of materials that fit into each category.--Rwilliams354 (talk) 14:53, 27 November 2016 (EST)
Conductors: Gold, Iron, Silver, Copper, Aluminum, Tin Semiconductors: Silicon, Germanium Insulators: Glass, Porcelain, Rubber, Cloth, Paper, Air
Semiconductors
Semiconductors are materials that have a conductivity in-between that of an insulator and a conductor. However, as temperature increases, unlike in most metals, the conductivity of semiconductors increases.
Temperature Dependence
As temperature increases, the electrical resistivity of metals increases. This is a reason why when computers heat up, they tend to slow down. Some materials exhibit superconductivity at extremely low temperatures. Below a certain temperature, resistivity vanishes, such as Pb at 7.20 K.
Equations
Maxwell's Equation for Electric Conductivity'--Rwilliams354 (talk) 14:13, 27 November 2016 (EST)
J=(conductivity)E --Rwilliams354 (talk) 14:13, 27 November 2016 (EST)
J= Electric Current Density E= Electric Field
Electric current density can be thought of as the electric current per cross sectional area of a specific material. Therefore this formula relates to each material differently. Every material has a specific conductivity associated with it, and this conductivity can help describe the electric field in each material. For example, materials such as copper and silver have extremely high electric conductivity and therefore in order to not have an almost infinite electric current density we can approximate the electric field inside the metals to be zero. This equation is essentially the proof for all metals having a zero electric field on the inside. --Rwilliams354 (talk) 14:13, 27 November 2016 (EST)
Poulliet's Law
R=ρℓ/A
R = Electric Resistance ρ = Electric Resistivity ℓ = Length A = Cross-Sectional Area
Poulliet's Law states that a given materials resistance will increase in length, while it will decrease with an increase in Area.
Conductivity in Real Life
Conductors are used to carry electricity, as well as electrical signals in circuits. Complementary metal–oxide–semiconductors, or CMOS for short, are the foundational building block of gate based logic circuits, that make up the majority of all modern electronics. CMOS circuits are composed of a combination of p-type and n-type semiconductors. These semiconductors will change their conductivity, based on the applied voltage, allowing for logic of 0's and 1's, or low voltage and high voltage, to be transferred through logical circuits. This allows us to apply boolean logic to circuits, such as AND and OR logic, or even create an amalgamation of AND's and OR's to create electronics, such as multiplexors, switches, latches, registers, decoders, encoders, etc.
https://www.youtube.com/watch?v=ODbgKXFED5o--Rwilliams354 (talk) 14:13, 27 November 2016 (EST)
History
Stephen Gray, Father of Conduction--Rwilliams354 (talk) 14:15, 27 November 2016 (EST)
Born 1666 in Canterbury, England. Died 1736 in London, England.--Rwilliams354 (talk) 14:15, 27 November 2016 (EST)
Gray was an innovative thinker who performed many a experiment including work with the transmission of electricity. One day while performing one of his experiments, unbeknownst to him he discovered the difference between insulators and conductors. He was working with transmitting electricity and he changed the transmission wire from silk to brass wire when he noticed that electricity passes completely different in brass than it does in silk. After said discovery, Gray spend the next 3 years with the help of friends and family doing more research in similar topics, and with this research some might say solidified his name as the father of conduction.--Rwilliams354 (talk) 14:15, 27 November 2016 (EST)
Further reading
Georgia Tech Research and Information regarding conduction in School of Materials Science and Engineering http://www.mse.gatech.edu/research/equipment-facilities/electrical-properties-materials-and-devices--Rwilliams354 (talk) 14:55, 27 November 2016 (EST)
External links
References
History: "Gray, Stephen." Complete Dictionary of Scientific Biography. . Encyclopedia.com. 25 Nov. 2016 <http://www.encyclopedia.com>.--Rwilliams354 (talk) 14:13, 27 November 2016 (EST)
Equations: "Conductivity." Maxwells-Equations.com, 2012. http://maxwells-equations.com/materials/conductivity.php --Rwilliams354 (talk) 14:10, 27 November 2016 (EST)