resistancetemperature

Resistancetemperature is a term that describes how a material’s electrical resistance changes with temperature. In practice, the widely used concept is the temperature coefficient of resistance (TCR), which quantifies the relative change in resistance per degree of temperature change. The resistancetemperature relationship can be described by simple models for practical sensing and analysis.

The basic linear model expresses the resistance at temperature T as R(T) = R0 [1 + α (T − T0)], where R0 is the resistance at a reference temperature T0 and α is the linear temperature coefficient of resistance. For most metals, α is positive, meaning resistance increases with temperature. Typical metals and alloys used in resistance thermometers have α values on the order of a few thousandths per degree Celsius (for example, platinum has α ≈ 0.00385 /°C near room temperature). Semiconductors, on the other hand, often exhibit a negative TCR, with resistance decreasing as temperature rises, and their dependence can be strongly nonlinear.

Over wider temperature ranges the linear approximation breaks down, and the relationship becomes nonlinear. In such cases, higher-order models or material-specific equations are used. Thermistors illustrate strong nonlinearity: negative-temperature-coefficient (NTC) thermistors show rapidly decreasing resistance with temperature, while positive-temperature-coefficient (PTC) thermistors increase resistance with temperature in a nonlinear fashion.

Applications commonly rely on resistancetemperature behavior to measure temperature. Resistance thermometers (RTDs) and thermistors are used in instrumentation, control systems, and various sensors. Key considerations include calibration, self-heating effects from measurement current, aging, and mechanical strain, all of which can alter the observed resistancetemperature response. See also temperature coefficient of resistance, RTD, and thermistor.