Variable resistors are electronic components whose resistance can be adjusted, allowing for control over current flow in a circuit.
Understanding Variable Resistors
A variable resistor, as the name suggests, is a resistor whose resistance value can be changed. Unlike fixed resistors, which have a single, pre-determined resistance, variable resistors allow the user to manually adjust the resistance. This adjustment alters the current flowing through the circuit.
How Variable Resistors Work
They typically consist of a resistive element and a sliding or rotating contact (wiper). Moving the wiper along the resistive element changes the effective length of the resistive path, and thus the resistance.
Types of Variable Resistors
There are two main types of variable resistors:
- Potentiometers: These have three terminals. Two terminals are connected to the ends of the resistive element, and the third is connected to the wiper. Potentiometers act as adjustable voltage dividers.
- Rheostats: These have two terminals. The wiper is connected to one terminal, and one end of the resistive element is connected to the other. Rheostats are used to directly control the current in a circuit. Sometimes a potentiometer can function as a rheostat by only using the wiper and one end connection.
Applications of Variable Resistors
Variable resistors are used in a wide variety of applications, including:
- Volume Controls: Potentiometers are commonly used to adjust the volume in audio equipment.
- Light Dimmers: Rheostats or potentiometers can be used to control the brightness of lights.
- Calibration: Variable resistors are used to calibrate electronic circuits and instruments.
- Control Systems: They can be used as sensors in control systems, such as position sensors.
Potentiometers vs. Rheostats
| Feature | Potentiometer | Rheostat |
|---|---|---|
| Number of Terminals | Three | Two |
| Functionality | Adjustable voltage divider | Variable resistance for current control |
| Typical Use | Voltage division, signal attenuation | Current limiting, power control |
| Connections | All three terminals typically used | Wiper and one end terminal used |
Variable resistors provide a crucial element of control and flexibility in electronic circuits, allowing for precise adjustments to voltage and current.
