Ohmsches

Ohmsches Gesetz, in English commonly Ohm's law, is a fundamental relation in electrical circuits. It states that the current I through a conductor between two points is proportional to the voltage V across the two points and inversely proportional to the resistance R, expressed as V = I R. The law describes the behavior of many materials and devices that exhibit a linear current–voltage relationship, known as ohmic conductors, at a given temperature.

The concept is named after Georg Simon Ohm, who published the relation in 1827. The term ohm is the SI unit of electrical resistance; one ohm corresponds to a conductor that, when a constant potential difference of one volt is applied, yields a current of one ampere, without internal emf generation.

Extensions and limitations: In alternating current (AC) circuits, the law generalizes to V = Z I, where Z is the complex impedance that combines resistance and reactance. The simple V = I R form holds for linear, temperature-stable resistors. It does not apply to non-linear components such as diodes or transistors, nor to materials whose resistance changes significantly with temperature or frequency. Temperature typically affects resistance, often increasing R for metals. In high-frequency or specialized contexts, effects like skin depth and superconductivity modify the effective relationship.

Power relations follow from Ohm's law: P = V I = I^2 R = V^2 / R. The law remains a cornerstone of circuit analysis, design, and education, underpinning techniques for calculating currents, voltages, and resistances in linear networks.