A resistor is a passive two-terminal electrical component that creates resistance in the flow of electric current. It is a critical piece in just about every circuit and is used to limit or regulate the flow of electric current in electrical circuits. The resistance of a resistor is measured in ohms, and it can be used for many purposes, including limiting electric current, voltage division, heat generation, matching and loading circuits, gain control, and setting time constants. Resistors can be found in almost all electrical networks and electronic circuits. They are commonly used to reduce current flow, adjust signal levels, divide voltages, bias active elements, and terminate transmission lines, among other uses.
Resistors can be fixed or variable. Fixed resistors have resistances that only change slightly with temperature, time, or operating voltage. Variable resistors can be used to adjust circuit elements, such as a volume control or a lamp dimmer, or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors can be fabricated in a variety of ways, including carbon composition, metal film, metal oxide film, and wirewound.
The international IEC symbol for a resistor is a rectangular shape with leads at each end, while the ANSI standard in the USA represents a fixed resistor as a zigzag line. Resistors are commonly used in digital multimeters, amplifiers, telecommunication, oscillators, modulators, demodulators, and transmitters.
