What are Rheostats and How Do They Work?

For an electrical circuit to properly manage current for various components, there are often times in which current needs to be restricted. Generally, current restriction is achievable through increasing the resistance of a circuit, or one may simply reduce the amount of voltage flowing through it. With a device known as a rheostat, the flow of current within an electrical circuit may be controlled through the means of increasing or decreasing resistance.

A rheostat is a form of potentiometer, that of which is a three-terminal resistor that contains a sliding or rotating contact. When two terminals of the device are used alongside a wiper, the potentiometer is considered to be a rheostat or variable resistor. For electrical circuits, rheostats are the most common method for continuously adjusting resistance. To do this, the rheostat simply adjusts its length to affect the magnitude of current.

To connect a rheostat to a circuit for resistance control, two terminals are attached to the ends of a resistive element known as a track, and the final terminal is fixed to a sliding wiper. The movement of the wiper is what allows for changes to be made to resistance, often being adjusted back and forth on the resistive path. Rheostats are commonly found in the form of wire wound variations, and the resistive component of the rheostat is most often constructed from a coil of wire or thin carbon film. If the rheostat is a wire wound type, the core is typically made from a ceramic, acting as an insulator for heat mitigation. Meanwhile, a nichrome wire will often serve as the winding for the device.

For the wiper to be capable of adjusting resistance, it is moved closer or farther from the output terminal so that the restive path changes. As such, moving the wiper towards the input terminal will cause current to travel farther on the resistive element, thus cutting down on the amount of voltage that leaves the device. It is important to note that adjusting the wiper does not have any effect on the resistance of the wire or resistive path itself. Rather, it temporarily adjusts the length of the resistive path so that resistance is changed as needed.To operate the wiper, many rheostats will have an external knob that may be turned.

Rheostats can come in two types, those being rotary and linear rheostats. Rotary rheostats are notable for their circular or angled resistive elements, and the wiper may be adjusted in a rotary manner. As their design allows for more compact construction, such types are the most common for the means of saving space within a device. A linear rheostat, on the other hand, may have a cylindrical resistor element while its wiper is adjusted in a linear manner. While larger than the rotary rheostat, linear types may still be found in numerous applications such as for laboratory devices which are used for either research or teaching. For common rheostat applications in general, such devices may be found in light dimmers, volume controls, or motor speed controls.

When you are in the market for reliable rheostat components, potentiometer devices, or other electrical circuit parts, there is no better alternative to Methodical Purchasing. On our website, customers can find NSN parts, aviation components, electrical connectors, and IT hardware that has been sourced from leading global manufacturers that we trust. To guarantee the quality of our offerings, we subject our inventory to rigorous quality assurance testing and inspection, and all orders ship alongside their qualifying certifications or manufacturing trace documentation as applicable. Get started today with a competitive quote for your comparisons when you fill out and submit an RFQ form as provided on our website.


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