Overview
This lecture explains the structure, working principles, and common uses of a potentiometer, a manually adjustable variable resistor found in many electronic circuits.
Potentiometer Structure
- A potentiometer is an analog device with three terminals: two fixed outer terminals and one variable middle terminal (wiper).
- The resistive element forms an arc within the device, with maximum resistance between the two outer terminals.
- Turning the knob moves the wiper across the resistive element, changing the resistance value.
Working Principle
- Connecting the two outer terminals to a multimeter shows the maximum resistance of the potentiometer.
- Measuring between the wiper and one outer terminal gives a resistance that varies with the wiper's position.
- The combined resistance between the wiper and each outer terminal always equals the potentiometer's maximum resistance.
Potentiometer Applications
- Using only the wiper and one outer terminal, the potentiometer acts as a variable resistor (rheostat).
- Example: Controlling LED brightness by adjusting resistance, which changes the current through the LED.
- Using all three terminals, the potentiometer acts as a voltage divider.
- Example: Controlling a DC motor’s speed by varying the voltage supplied to the motor based on the wiper position.
Key Terms & Definitions
- Potentiometer — A variable resistor that allows manual adjustment of resistance by turning a knob.
- Wiper — The sliding contact in a potentiometer that moves across the resistive element.
- Resistive Element — The component inside the potentiometer providing electrical resistance.
- Voltage Divider — A circuit configuration using three potentiometer terminals to provide a variable output voltage.
Action Items / Next Steps
- Review how to connect potentiometers as variable resistors and voltage dividers in circuit diagrams.
- Practice measuring and adjusting resistance with a multimeter.