Rheostats

Adjust and control the current in an electrical circuit with a rheostat. These variable resistors are used to control current without interrupting the flow, making them a useful addition to a circuit.

Whether you need a rheostat switch or you are searching for a specific voltage, such as a 12-volt option, choose from the rheostats at RS. We stock high-quality products from leading manufacturers.

To find out more about rheostats, read on.

What are rheostats?

A rheostat is a variable resistor that is used where the current in an electric circuit needs to be adjusted. This adjustment of the current flowing through the circuit is done without interrupting the power supply. They are a common electromechanical variable resistor and when in operation, the ohmic resistance value is adjusted manually by the user.

How do rheostats work?

In terms of their structure, rheostats are very similar in many ways to the potentiometer, which is another type of variable resistor. However, unlike a potentiometer, which has three terminals, a rheostat uses two terminals.

The first of these terminals - or connections - is for the resistive strip and the other terminal is for the wiper, which is the sliding contact. There is no third terminal in most rheostats and even if a third is present only the two are used.

As with potentiometers, the wiper (or slider) is moved across the resistive strip, and this varies the resistance. Rheostats are typically wire-wound resistors made of a coil of wire or thin carbon film. This resistive wire is wound around a ceramic core that offers insulation. The wiper slides over these windings.

The types of rheostats

There are two types of rheostats:

• Rotary

Rotary rheostats are often referred to as circular rheostats. Here, the resistive element looks like a circle or is set out in a circular form. To follow this shape, the wiper moves around in a rotary style. These are the more common type of rheostat and are often preferred over linear variants because they are more compact.

• Linear

Linear rheostats are often referred to as cylindrical rheostats due to their shape. Here, the wiper moves in a linear fashion.

What are the differences between a rheostat and a potentiometer?

There are many similarities between rheostats and potentiometers. They are both types of variable resistors and they have similar form and functionality. But the differences must be highlighted to know which of the two are needed for a job.

We have already mentioned that rheostats are two-terminal variable resistors. Unlike potentiometers, which control the voltage, they adjust the current. They are often used to control higher currents because having one less terminal means they are more mechanically robust, especially when attached to a printed circuit board (PCB).

Another main difference between the two is that a rheostat only offers a linear taper. Potentiometers can have either a linear or logarithmic taper.

Where are rheostats used?

While most applications require a rotary rheostat, linear rheostats are often used in laboratories. Rheostats - mostly rotary rheostats - are used where a high voltage is needed. For instance, they are often found in circuits where light intensity needs to be altered. Increasing the rheostat's resistance will reduce the electric current flowing to the bulb, decreasing the light intensity.

They are also used to raise or reduce speed in an electric motor and power heaters and ovens. This makes them useful in culinary and kitchen settings.

Why choose RS for your rheostats?

At RS, we stock a range of rheostats that are designed to help you successfully control the current flowing in a circuit. We are a leading authorized distributor in North America and stock rheostats by leading names including Ohmite, TE Connectivity, and Vishay Dale.

If have any questions, our team is on hand to help. Get in touch and we can guide you through the products. You can also find advice in our expert content hub.