The device with a three-terminal configuration is called a variable resistor. Rheostat and potentiometer both come under the category of variable resistors. The function of the variable resistor is to provide the variable amount of resistance within an electrical circuit. Variable Resistors consists of a knob that helps it to regulate and modify the output resistance. These types of resistors have become one of the oldest types. Modern variable resistors come with small bolts called trimpots. These trimpots can be tightened or loose according to the applications.
Rheostat vs Potentiometer
The main difference between rheostat and Potentiometer is that Rheostat is a special resistor that consists of two terminals and it creates a relation between the wiper and one side. A potentiometer is a device consisting of three terminals with an adjusting knob for regulating the resistance. The work of a rheostat is to change the resistance according to use. While the work of a potentiometer is that it is used as a measuring device.
A rheostat is a device that is used basically to regulate the resistance i.e., either to reduce or increase the flow of current manually. It is a very common kind of variable resistor. It can be said as the power controlling instruments and are used in various appliances like oven, heaters for managing the intensity of light and monitor the speed. But they are very low efficient so they are now not used much. It is a two-terminal device that checks the amount of current flowing within the device.
A potentiometer is a device that comes with a voltage divider that can be rotated or slide. It is a three-terminal device. If only two terminals are used then a potentiometer becomes a rheostat. A potentiometer is used as a measuring device. It is used to measure the voltage of an electrical device. It can also be used to control the volumes of electrical devices like audio speakers. It is operated via joystick also called position transducers.
Comparison Table Between Rheostat and Potentiometer
| Parameters of Comparison | Rheostat | Potentiometer |
| Made of | Various materials like and carbon disks, fluids and metal ribbon. | Resistive elements like cermet, graphite, wire, and carbon particles. |
| Use | Vary resistance | Measuring instrument |
| Function | Control the flow | Voltage dividing |
| Connection | Serial | Parallel |
| Flexibility | Cannot be used as Potentiometer. | Can be used as a rheostat. |
| Voltage Dividing | Cannot divide | Can divide |
What is Rheostat?
A rheostat is used to vary the flow of current in an electrical circuit. It is controlled manually by increasing or decreasing the resistance. It can change the resistance without any disturbance or interruption. They are also used to control devices like controlling the intensity of heat as used in heaters and ovens. But they are very low-efficient. Because of it they are no longer used for these purposes. Now Rheostat is used for calibrating and tuning in the circuits.
The construction of a rheostat is very much similar to a potentiometer. A rheostat cannot become a potentiometer. Because it is a small part of a potentiometer. It has only two connections one is for sliding i.e., wiper and the other is for resistive element. There are majorly three types of Rheostat. Preset, Rotary and Linear. Preset Rheostat is used in printed circuit boards usually. Rotary is used when the slider or resistive element of the rheostat moves in a circular direction.
A linear rheostat is used when the slider and resistive element moves in a linear or straight direction. There are various applications of rheostat like it is used in the devices where high voltage is required, it is also used to dim lights as it can change the intensity of lights and it is used to control the volume of a device like radio or speed of a motor. It forms a serial connection and the flowing current can be controlled by it.
What is Potentiometer?
There are various terms through which different types of the potentiometer is used to describe in electronic industry. It includes a trim pot, slide pot and thumb pot. The potentiometer consists of three terminals, two of them is connected via resistive element and the third is connected to a wiper. The output voltage of a potentiometer is determined by the position of a wiper. It acts as a measuring device and controls the electromotive force of a given cell.
A potentiometer can also act as a rheostat if only two terminals are connected. Resistors in a potentiometer can provide a fixed amount of resistance that can allow or block the flow of a current in the circuit. It can also provide a voltage drop by Ohm’s law also called Voltage Dividing. Two types of potentiometers can be adjusted manually. They are Linear and Rotary Potentiometer. Linear is when the wiper moves in a straight direction. Rotary is when the wiper moves in a rotating direction.
There are various uses of a Potentiometer. But the three main uses are comparing the emf of a standard cell with a battery cell, measuring the internal resistance of a battery cell and measuring the voltage of a circuit in a branch. It cannot divide voltage. It is connected with parallel in an electrical circuit. It is used to control the volume in audio systems and acts as a transducer in controlling television.
Main Differences Between Rheostat and Potentiometer
- A rheostat is made up of various materials like and carbon disks, fluids and metal ribbons. A Potentiometer is made up of resistive elements like cermet graphite, resistance wire, and carbon particles.
- The use of a rheostat is to vary the resistance in a circuit. The use of a potentiometer is to measure the instruments or components.
- The function of a rheostat is to control the flow of a current. The function of a potentiometer is that it is used for dividing voltage.
- The connection used in a rheostat is serial. The connection used in a potentiometer is parallel.
- A rheostat cannot be used as Potentiometer. A potentiometer can be used as a rheostat.
- A rheostat cannot divide voltage. A potentiometer can divide voltage.
Conclusion
Both rheostat and potentiometer is a type of resistor. A potentiometer can act as a rheostat. It is a whole where rheostat is also a part of it. Both the devices are used t monitor the current but they have different features. Like potentiometer controls voltage and rheostat control current. Both use the sliding motion called wiper to vary the voltage and current according to its functions and applications in the circuit. A potentiometer is generally used to control the low power. While rheostat is used to control the high power. A rheostat is a variable resistor while a potentiometer can act as a sensor.
References
- https://aip.scitation.org/doi/abs/10.1063/1.1751472
- https://aapt.scitation.org/doi/abs/10.1119/1.1934883