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The temperature coefficient is the relative change of a physical property when the temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 is changed by 1 K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
.

In the following formula, let R be the physical property to be measured and T be the temperature at which the property is measured. T0 is the reference temperature, and ?T is the difference between T and T0. Finally, a is the (linear) temperature coefficient.






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The temperature coefficient is the relative change of a physical property when the temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 is changed by 1 K
Kelvin

The kelvin is a Units of measurement of temperature and is one of the seven SI base units. The Kelvin scale is a Thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero ....
.

In the following formula, let R be the physical property to be measured and T be the temperature at which the property is measured. T0 is the reference temperature, and ?T is the difference between T and T0. Finally, a is the (linear) temperature coefficient. Given these definitions, the physical property is:

Here a has the dimension
Dimension

In mathematics, the dimension of a space is roughly defined as the minimum number of coordinates needed to specify every point within it. For example: a point on the unit circle in the plane can be specified by two Cartesian coordinates but one can make do with a single coordinate , so the circle is 1-dimensional even though it exists in...
s of an inverse temperature (1/K or K-1).

This equation is linear
Linear

The word linear comes from the Latin word linearis, which means created by lines.In mathematics, a linear map or function f is a function which satisfies the following two properties......
 with respect to temperature. For quantities that vary polynomial
Polynomial

In mathematics, a polynomial is an expression constructed from variables and constants, using the operations of addition, subtraction, multiplication, and constant non-negative whole number exponents....
ly or logarithm
Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
ically with temperature, it may be possible to calculate a temperature coefficient that is a useful approximation for a certain range of temperatures. For quantities that vary exponentially
Exponential growth

Exponential growth occurs when the growth rate of a mathematical function is proportionality to the function's current value. In the case of a discrete domain of definition with equal intervals it is also called geometric growth or geometric decay ....
 with temperature, such as the rate of a chemical reaction
Arrhenius equation

The Arrhenius equation is a simple, but remarkably accurate, formula for the temperature dependence of the rate constant, and therefore, rate of a chemical reaction....
, any temperature coefficient would be valid only over a very small temperature range.

Temperature coefficient of electrical resistance


The temperature dependence of electrical resistance
Electrical resistance

The electrical resistance of an object is a measure of its opposition to the passage of a steady electrical current. An object of uniform cross section will have a resistance proportional to its length and inversely proportional to its cross-sectional area, and proportional to the resistivity of the material....
 and thus of electronic devices (wire
Wire

A wire is a single, usually cylinder , elongated string of metal. Wires are used to bear mechanical Structural loads and to carry electricity and telecommunications Wiktionary:signal....
s, resistor
Resistor

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s) has to be taken into account when constructing devices and circuits
Electrical network

An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches....
. On the other hand, this property is used in devices such as thermistor
Thermistor

A thermistor is a type of resistor with electrical resistance proportional to its temperature. The word is a portmanteau of Thermal and resistor....
s.

The temperature dependence of conductors
Electrical conductor

In science and Electrical engineering, an electrical conductor is a material which contains movable electric charges. In metallic conductors, such as copper or aluminum, the movable charged particles are electrons ....
 is to a great degree linear, that of a semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
 is however exponential: R(T) = a × exp(b/T).

Coefficient of thermal expansion

The physical dimensions of matter can be affected by temperature. The coefficient of thermal expansion
Coefficient of thermal expansion

When the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds....
 for a given sample of matter can be used to approximate its change in volume given a change in temperature. A similar coefficient, the linear thermal expansion coefficient, is also often used to measure the change of length of an object in one-dimension.

The coefficient of thermal expansion is often used to develop thermometers. Here lengths of materials can express temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
. The coefficient is also used for several types of thermostats.

Temperature coefficient of elasticity

The elastic modulus
Elastic modulus

An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically when a force is applied to it....
 of elastic materials varies with temperature, typically decreasing with higher temperature.

Temperature coefficient of reactivity


In a nuclear reactor, the temperature coefficient of reactivity is a measure of the change in reactivity, or the change in power, brought about by a change in temperature of the reactor components or the reactor coolant. In water-cooled nuclear reactors, the predominant reactivity changes are brought about by changes in the temperature of the coolant water. In this case, the temperature coefficient is negative, which means that an increase in coolant temperature causes a decrease in reactivity, and vice-versa.