The variable resistor is a resistor whose value can be accustomed by turn a shaft or sliding a control. They are also referred to as potentiometers or rheostats and permit the resistance of the device to be altered by hand. A rheostat is a variable resistor with two terminals, one sliding and one fixed. It is utilized with high currents. The term rheostat is usually reversed for higher-powdered device, above about ½ watt. A potentiometer is a common type of variable resistor; one common use is as volume controls on audio amplifiers and other forms of amplifiers.
CLASSIFICATIONOF VARIABLE RESISTORS:
These resistors can be categorized on the basis of material used and application. On the basis of application they are known as the general purpose and they are of precision type. But on the basis of resistive material they are categorized as:
(a) Carbon composition resistors
(b) Wire wound resistors
(c) Cermets resistors
(d) Multi-turn resistors
(e) Multi-turn potentiometers