Editing Temperature coefficient (section)

==Negative temperature coefficient==
{{Confusing section|reason=it's unclear whether this refers to a general negative temperature coefficient or concerning electrical conductivity specifically|small=no|date=January 2016}}
Most [[ceramic]]s exhibit negative temperature dependence of resistance behaviour. This effect is governed by an [[Arrhenius equation]] over a wide range of temperatures:
:<math>R = Ae^{\frac{B}{T}}</math>

where ''R'' is resistance, ''A'' and ''B'' are constants, and ''T'' is absolute temperature (K).

The constant ''B'' is related to the energies required to form and move the [[charge carrier]]s responsible for electrical conduction{{snd}} hence, as the value of ''B'' increases, the material becomes insulating. Practical and commercial NTC [[resistor]]s aim to combine modest resistance with a value of ''B'' that provides good sensitivity to temperature. Such is the importance of the ''B'' constant value, that it is possible to characterize NTC [[thermistor]]s using the B parameter equation:
:<math>R = r^{\infty}e^{\frac{B}{T}} = R_{0}e^{-\frac{B}{T_{0}}}e^{\frac{B}{T}}</math>

where <math>R_{0}</math> is resistance at temperature <math>T_{0}</math>.

Therefore, many materials that produce acceptable values of <math>R_{0}</math> include materials that have been alloyed or possess variable '''negative temperature coefficient''' (NTC), which occurs when a physical property (such as [[thermal conductivity]] or [[electrical resistivity]]) of a material lowers with increasing temperature, typically in a defined temperature range. For most materials, electrical resistivity will decrease with increasing temperature.

Materials with a negative temperature coefficient have been used in [[floor heating]] since 1971. The negative temperature coefficient avoids excessive local heating beneath carpets, [[bean bag]] chairs, [[mattress]]es, etc., which can damage [[Wood flooring|wooden floors]], and may infrequently cause fires.