what is a variable resistor

A variable resistor is a type of resistor whose electric resistance value can be adjusted. It is an electro-mechanical transducer that works by sliding a contact (wiper) over a resistive element. There are two basic types of variable resistors: potentiometers and rheostats. A potentiometer is a variable resistor with three terminals that functions as a resistive divider. It is typically used to generate a voltage signal depending on the position of the potentiometer, which can be used for a wide variety of applications including amplifier gain control, measurement of distance or angles, and tuning of circuits. When only two terminals are used, it functions as a variable resistance and is called a rheostat. Rheostats usually have two connections, one fixed and the other moveable, and have a limited range of values and a high current-handling capability. Potentiometers, on the other hand, have a wide range of values but usually have a limited current-handling capability. Digital variable resistors also exist, which can be controlled electronically instead of by mechanical action. They can change resistance in discrete steps and are often controlled by digital protocols such as I2C or by simple up/down signals.