Ohm's Law

Formula

Description

Ohm's Law is the foundational relationship in electronics, first published by Georg Simon Ohm in 1827. It states that the voltage across a conductor is directly proportional to the current flowing through it, with the constant of proportionality being the resistance. This linear relationship holds for ohmic materials like metals and carbon resistors at constant temperature, but breaks down for semiconductors, diodes, and other nonlinear devices. It is the starting point for nearly every circuit analysis technique including Kirchhoff's laws, nodal analysis, and mesh analysis.

Variables

• V — Voltage in volts (V), the electrical potential difference
• I — Current in amperes (A), the flow of electric charge
• R — Resistance in ohms (Ω), opposition to current flow

Practical Notes

Resistance increases with temperature for most conductors. For precise work, account for the temperature coefficient of the resistor material. Ohm's Law applies to DC circuits directly and to AC circuits when using complex impedance in place of resistance.