Ohmtörvénye

Ohmtörvénye, commonly known in English as 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 by the equation V = IR. The constant of proportionality is the resistance, measured in ohms (symbol Ω). For a given material and temperature, this linear relation holds for many conductors, particularly metallic resistors, within their ohmic region.

The law is named after Georg Simon Ohm, who described the relationship in 1827 from systematic experiments on electrical circuits. It became a cornerstone of circuit theory and electronics, enabling practical analysis of simple and complex networks.

Applications and extensions: Ohm's law is used to calculate currents, voltages, and resistances in direct current (DC) circuits and in basic alternating current (AC) circuits. In series circuits, the current is the same through all components and the total resistance is the sum of individual resistances (R_total = ΣR_i). In parallel circuits, the voltage across each branch is the same and the reciprocals of resistances add (1/R_total = Σ(1/R_i)). Power relations follow as P = VI = I^2R = V^2/R.

Limitations: The simple V = IR form applies to linear, ohmic devices under constant temperature. Real materials may have resistance that varies with temperature, illumination, or other conditions, and non-ohmic components (such as diodes and transistors) do not follow a linear current–voltage relation. In AC analysis, the law generalizes to impedance: V = IZ, with Z potentially complex.