resistansfunktion

Resistansfunktion is a term used in physics and electrical engineering to describe how the electrical resistance of a component or circuit depends on one or more variables. The concept applies to simple linear resistors as well as to devices whose resistance changes with conditions such as temperature, current, voltage, or time. A resistansfunktion expresses R as a function of these variables: R = f(variables).

Typical forms include geometry-based resistance: R = ρ L / A, where ρ is the resistivity, L the length, and A the cross-sectional area. If ρ depends on temperature, resistance becomes a temperature-dependent function R(T) = ρ(T) L / A. A common approximation for metals is ρ(T) ≈ ρ0 [1 + α (T - T0)], with α the temperature coefficient of resistivity.

Nonlinear or temperature-sensitive devices may have resistances that depend on current or voltage, such as thermistors or varistors. In such cases the resistansfunktion is nonlinear, for example R = f(I) or R = f(V, I, T). In networks, the effective resistance between two nodes is a function of the network topology and component values.

Applications include circuit design, sensor calibration, thermal modeling, and simulation of electrical systems. The concept complements Ohm's law and the broader notion of impedance, by focusing on the resistance part and its potential dependencies.