Variable Resistors and Fixed Resistors

There are two kinds of resistors, FIXED and VARIABLE RESISTORS. The fixed resistor will have one value and will never change (other than through temperature, age, etc.).

The tapped resistor has several fixed taps and makes more than one resistance value available. The sliding contact resistor an adjustable collar that can be moved to tap off any resistance within the ohmic value range of the resistor.

There are two types of variable resistors , one called a POTENTIOMETER and the other a RHEOSTAT.

An example of the potentiometer is the volume control on your radio, and an example of the rheostat is the dimmer control for the dash lights in an automobile.

There is a slight difference between them. Rheostats usually have two connections, one fixed and the other moveable. Any variable resistor can properly be called a rheostat. The potentiometer always has three connections, two fixed and one moveable.

Generally, the rheostat has a limited range of values and a high current-handling capability. The potentiometer has a wide range of values, but it usually has a limited current-handling capability.

Potentiometers are always connected as voltage dividers.

Refer to the article on (Resistors) for an illustration.

(back) (top) (next) (return to resistance page)