Rheostats: A Type Of Variable Resistors

Rheostats: A Type Of Variable Resistors

RHEOSTAT

A rheostat is a type of variable resistor that is used to control electric current flowing in a circuit. The word rheostat was coined by an English scientist called Sir Charles Wheatstone. it is derived from the Greek word “rheos” and “statis” which means a stream controlling device or a current controlling device. They are used to vary the resistance in a circuit without interruption. Just like potentiometer, rheostat have 3 terminals for connections. It uses only two out of the three terminals for connections. The first connection is made to one end of the resistive element and the other to the wiper. Rheostat is made up of a resistive element (wire is wound around an insulating ceramic core) and a wiper (sliding contact) slides over the windings.

Rheostat Symbol

Rheostat Symbol

Types Of Rheostats

There are many types of rheostats. The rotary type is the most used in power control applications like the control speed of a motor. Just like potentiometers, multi-gang types are also available. They are used to regulate multiple applications in parallel or to increase the power rating without interruption of power. Freely rheostats can be fitted with a mechanical stop to limit the minimum or maximum resistance.

Slide rheostats are also available and usually used for education and in laboratory environments. Both Linear and slide rheostats are made of resistive wire wound on an insulating cylinder. A sliding contact is often used to increase or decrease the resistance, thereby increases or decreases the current flowing in the circuit.

Applications Of Rheostat

Rheostats were usually used as power control devices, for example,used as a dimmer i.e  to control light intensity, speed of motors, heaters and ovens. Rheostats are often used for tuning and calibration in circuits. Motor controllers also use rheostats to control a motor’s  velocity by limiting the flow of current. Rheostats are also used in many small devices likeblenders, mixers, fans, and power tools. Furthermore,it can be used as a test device to give a reference resistance value(s).

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