Changes

==Etymology==

==Etymology==

[[Latin]] insula

[[Latin]] insula

*Date: circa [http://www.wikipedia.org/wiki/18th_Century 1741]

*Date: circa [https://www.wikipedia.org/wiki/18th_Century 1741]

==Definition==

==Definition==

*to place in a detached situation : [[isolate]]; especially : to separate from conducting [[bodies]] by means of nonconductors so as to prevent transfer of [[electricity]], [[heat]], or [[sound]]

*to place in a detached situation : [[isolate]]; especially : to separate from conducting [[bodies]] by means of nonconductors so as to prevent transfer of [[electricity]], [[heat]], or [[sound]]

==Description==

==Description==

[[Electrical]] '''insulation''' is the [[absence]] of [http://en.wikipedia.org/wiki/Electrical_conduction electrical conduction]. Electronic [http://en.wikipedia.org/wiki/Electronic_band_structure band theory] (a branch of [[physics]]) [[predicts]] that a [[charge]] will [[flow]] whenever there are [[states]] available into which the [[electrons]] in a [[material]] can be excited. This allows them to gain [[energy]] and thereby move through the conductor (usually a metal). If no such states are available, the [[material]] is an insulator.

[[Electrical]] '''insulation''' is the [[absence]] of [https://en.wikipedia.org/wiki/Electrical_conduction electrical conduction]. Electronic [https://en.wikipedia.org/wiki/Electronic_band_structure band theory] (a branch of [[physics]]) [[predicts]] that a [[charge]] will [[flow]] whenever there are [[states]] available into which the [[electrons]] in a [[material]] can be excited. This allows them to gain [[energy]] and thereby move through the conductor (usually a metal). If no such states are available, the [[material]] is an insulator.

Most (though not all, see [http://en.wikipedia.org/wiki/Mott_insulator Mott insulator)] insulators are characterized by having a large [http://en.wikipedia.org/wiki/Band_gap band gap]. This occurs because the "valence" band containing the highest energy electrons is full, and a large energy gap separates this band from the next band above it. There is always some voltage (called the [http://en.wikipedia.org/wiki/Breakdown_voltage breakdown voltage]) that will give the [[electrons]] enough [[energy]] to be excited into this band. Once this voltage is exceeded, the [[material]] ceases being an insulator, and [[charge]] will begin to pass through it. However, it is usually accompanied by [[physical]] or [[chemical]] [[changes]] that permanently degrade the material's insulating properties.

Most (though not all, see [https://en.wikipedia.org/wiki/Mott_insulator Mott insulator)] insulators are characterized by having a large [https://en.wikipedia.org/wiki/Band_gap band gap]. This occurs because the "valence" band containing the highest energy electrons is full, and a large energy gap separates this band from the next band above it. There is always some voltage (called the [https://en.wikipedia.org/wiki/Breakdown_voltage breakdown voltage]) that will give the [[electrons]] enough [[energy]] to be excited into this band. Once this voltage is exceeded, the [[material]] ceases being an insulator, and [[charge]] will begin to pass through it. However, it is usually accompanied by [[physical]] or [[chemical]] [[changes]] that permanently degrade the material's insulating properties.

[[Materials]] that lack [[electron]] conduction are insulators if they lack other mobile [[charges]] as well. For example, if a liquid or gas contains ions, then the ions can be made to [[flow]] as an [[electric]] current, and the material is a conductor. [http://en.wikipedia.org/wiki/Electrolyte Electrolytes] and [http://en.wikipedia.org/wiki/Plasma_(physics) plasmas] contain ions and will act as conductors whether or not electron [[flow]] is involved.[http://en.wikipedia.org/wiki/Insulator_%28electrical%29]

[[Materials]] that lack [[electron]] conduction are insulators if they lack other mobile [[charges]] as well. For example, if a liquid or gas contains ions, then the ions can be made to [[flow]] as an [[electric]] current, and the material is a conductor. [https://en.wikipedia.org/wiki/Electrolyte Electrolytes] and [https://en.wikipedia.org/wiki/Plasma_(physics) plasmas] contain ions and will act as conductors whether or not electron [[flow]] is involved.[https://en.wikipedia.org/wiki/Insulator_%28electrical%29]

[[Category: Physics]]

[[Category: Physics]]