2r2

2R2 is a common marking used on electrical resistors to denote a resistance of 2.2 ohms. The letter R serves as the decimal point in this European-style numeric notation, allowing values with decimals to be printed without a separate dot. This convention is widely used across through-hole and surface-mmount resistor markings.

In resistor markings, several related values use the same pattern, such as 4R7 for 4.7 ohms, 1K0 for 1.0 kilohm, and 0R22 for 0.22 ohm. The basic value 2R2 may be accompanied by additional information on the component, such as tolerance (for example 5% or 1%) and power rating (such as 0.25 W, 0.5 W, or higher). The full marking on a component helps engineers select the correct part for a circuit without needing to measure it.

Typical uses for a 2.2-ohm resistor include current sensing, ballast, and load applications in power supplies, LED drivers, and audio or motor control circuits. The actual behavior depends on the resistance value and the power that the part must dissipate, calculated as P = I^2R or P = V^2/R. The physical size and construction (carbon film, metal film, or wire-wound) influence tolerance, temperature stability, and maximum safe current.

Caveats include that markings may vary by manufacturer and that the same alphanumeric string could appear in non-resistor contexts. When in doubt, consult the schematic or measure the component with a calibrated instrument.