A resistor is an electrical component and, in fact, is one of the most basic electrical components in use. Resistors, just as the name implies, introduce resistance into a circuit, which is measured in ohms. The ohms of a resistor is measured by determining the ratio of the voltage across the resistor to the current in the circuit. Basic resistors aren’t variable, so this measurement is generally a constant.
Resistors are differentiated by colored bands painted around the device. These bands correspond to numbers and, from those bands, electrical engineers and other individuals can determine exactly what the ohm rating of the resistor happens to be.
The most common types of resistors that are seen in practice are axial lead resistors, which consist of a small amount of resistive material through which a long metal lead is threaded, providing the contacts for the resistor to be attached to a printed circuit board or to an electrical circuit by other means.