Lämpökerroin

Lämpökerroin, also known as the temperature coefficient, is a property of a material or a physical system that describes how its properties change with temperature. This term is most commonly used in the context of electrical resistivity, but it can also apply to other physical quantities such as magnetic susceptibility, refractive index, and even the dimensions of a solid.

In electrical engineering, the temperature coefficient of resistance (TCR) quantifies the change in electrical resistance of a material per degree Celsius or Kelvin change in temperature. For most metallic conductors, the resistance increases with increasing temperature, meaning they have a positive TCR. Semiconductors, on the other hand, typically have a negative TCR, where their resistance decreases as temperature rises. This behavior is due to changes in the number of charge carriers available for conduction.

The TCR is often expressed as a percentage change per degree Celsius or as a value in units of per Kelvin (K⁻¹). For a given material and a temperature range, the relationship between resistance and temperature can often be approximated by a linear equation: R(T) = R₀(1 + α(T - T₀)), where R(T) is the resistance at temperature T, R₀ is the resistance at a reference temperature T₀, and α is the temperature coefficient of resistance.

Understanding the lämpökerroin is crucial in many applications. For example, in precision resistors, materials with a low TCR are preferred to minimize resistance drift with ambient temperature changes. Conversely, in some thermistor applications, materials with a large negative TCR are intentionally used to create temperature-sensitive resistors for measuring or controlling temperature. The lämpökerroin also influences the performance of electronic components, such as transistors and integrated circuits, by affecting their electrical characteristics.