What are Variable Resistors?
A variable resistor is an electronic component that allows you to change the amount of resistance in a circuit. Resistance is like the “opposition” to the flow of electricity. By changing the resistance, you can control the flow of electric current.
There are two common types of variable resistors:
- Potentiometers
- Rheostats
Let’s go into more detail about each one:
1. Potentiometers:
A potentiometer is a type of variable resistor with three terminals (connections). It’s usually used to adjust voltage in a circuit, and you often see them in things like volume controls on radios, TV sets, or in some power supplies.
- How it works: It has a sliding or rotating knob. When you turn the knob, you change the position of a wiper (a movable part inside the potentiometer). This wiper moves across a resistive track, which changes the resistance between the two outer terminals. The middle terminal gives a variable voltage depending on the wiper’s position.
- Example: When you adjust the volume on a radio, you’re using a potentiometer. Turning the knob adjusts the resistance, which changes the amount of voltage sent to the speaker, making it louder or softer.
2. Rheostats:
A rheostat is another type of variable resistor, but it has only two terminals (connections). It’s used to control the current flowing through a circuit rather than controlling voltage. It works by adjusting the resistance to allow more or less current to flow.
- How it works: Like the potentiometer, a rheostat has a moving part (a wiper), but since it only has two terminals, it’s typically used to control current flow in things like lamps or motors. When you move the wiper, you change the resistance, which adjusts the current flowing through the circuit.
- Example: A dimmer switch for lights uses a rheostat. When you turn the knob, it changes the resistance, which controls how much current flows to the light, making it brighter or dimmer.
Key Differences:
- Potentiometer: Three terminals; used to control voltage in a circuit.
- Rheostat: Two terminals; used to control current in a circuit.
Summary:
- Potentiometers are like adjustable voltage controllers with three connections.
- Rheostats are like adjustable current controllers with two connections.
Both are helpful for changing the flow of electricity in a circuit, but they are used in different ways depending on what you need to control—voltage (potentiometer) or current (rheostat).
