what is a resistor

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 electrical current in an electronic circuit. The resistors resistance limits the flow of electrons through a circuit, and it is a passive component, meaning it only consumes power and cannot generate it. Resistors are used for many purposes, including limiting electric current, voltage division, heat generation, matching and loading circuits, gain control, and setting time constants. They are commercially available with resistance values over a range of more than nine orders of magnitude. Resistors can be composed of various compounds and forms, and they are also implemented within integrated circuits. Fixed resistors have resistances that only change slightly with temperature, time, or operating voltage, while variable resistors can be used to adjust circuit elements or as sensing devices for heat, light, humidity, force, or chemical activity. The SI unit of resistor is Ohm, and the standard symbols for resistors are a rectangular shape with leads at each end or a zigzag line.