Rheostat vs. Potentiometer: Key Differences Explained
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This article explores the distinctions between rheostats and potentiometers, two devices used to vary resistance in circuits, thereby controlling current or voltage.
Rheostat
- A rheostat is a two-terminal device.
- It’s connected in series with the load and voltage source.
- The primary function of a rheostat is to vary the current in a circuit.
- As the wiper (adjustable contact) moves, the resistance changes. Moving the wiper “up” (in a typical schematic representation) increases resistance, while moving it in the opposite direction decreases it.
- Crucially, a rheostat must have a wattage rating sufficient to handle the maximum current () when the resistance () is at its minimum value.
Potentiometer
- A potentiometer is a three-terminal device.
- Its end terminals are connected across a voltage source.
- The third, variable arm (wiper) taps a portion of the applied voltage.
- The applied voltage () serves as the input to the two end terminals.
- The output voltage (), which is variable, is measured between the wiper and one of the end terminals.
- A potentiometer can function as a rheostat. This is achieved by using only the wiper terminal and one of the other terminals, leaving the third terminal unconnected and unused.