jännitevasteen

The term jännitevaste refers to the voltage response of an electrical circuit or device when it is subjected to a change in current or applied voltage. It is a key concept in the analysis of circuit behavior, especially in linear time‑invariant systems. In practical use, jännitevaste is often measured as the ratio of the induced voltage to the applied current, and can be expressed in ohms when the response is purely resistive. When reactive components such as capacitors or inductors are present, the voltage response becomes frequency dependent and is described by impedance, a complex quantity that includes both magnitude and phase.

Mathematically the jännitevaste V(ω) of a component or network can be written as V(ω) = Z(ω) I(ω), where Z(ω) is the impedance and I(ω) is the current at angular frequency ω. For a capacitor the impedance is Zc = 1/(jωC), and for an inductor Zl = jωL, where j is the imaginary unit. The magnitude of the jännitevaste determines how much voltage is dropped across the component for a given current, and the phase indicates how the voltage leads or lags the current.

In engineering practice jännitevaste data are used to design filters, match transmission lines, and predict noise performance. In signal processing it grounds the calculation of transfer functions and the stability analysis of control systems. In power systems the voltage response of transformers and generators is crucial for fault analysis and protection coordination. Though the term originates from Finnish, the underlying physics are universal, and the concept is referred to as voltage response or impedance in most international literature.