Potentiometer
A potentiometer (also known as a pot or potmeter) is defined as a 3 terminal variable resistor in which the resistance is manually varied to control the flow of electric current. A potentiometer acts as an adjustable voltage divider.
A potentiometer is a passive electronic component. Potentiometers work by varying the position of a sliding contact across a uniform resistance. In a potentiometer, the entire input voltage is applied across the whole length of the resistor, and the output voltage is the voltage drop between the fixed and sliding contact. A potentiometer has the two terminals of the input source fixed to the end of the resistor. To adjust the output voltage the sliding contact gets moved along the resistor on the output side.
This is different to a rheostat, where here one end is fixed and the sliding terminal is connected to the circuit. This is a very basic instrument used for comparing the emf of two cells and for calibrating ammeter, voltmeter, and watt-meter.
Khan Academy https://www.khanacademy.org/science/physics/
Potentiometer: Definition, Types, And Working Principle // Electrical4u https://www.electrical4u.com/potentiometer/