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Potentiometer Variable Resistor vs. Fixed Resistor: Which One Should You Use?

2025/8/4 11:17:11

When you build a circuit, you need the right resistor. A fixed resistor gives the same resistance all the time. A potentiometer variable resistor lets you change resistance as you go. In this article, we explain what each one is, show how a variablePotentiometer Variable Resistor vs. Fixed Resistor: Which One Should You Use? resistor pot works, and help you pick the best option for your project.

Definition of Variable Resistor

A variable resistor (or var resistor) lets you change its resistance by hand. A part with two terminals is a rheostat and it changes current. A part with three terminals is a potentiometer and it works as a voltage divider.

Definition of Fixed Resistor

A fixed resistor always has one resistance value. You use it when you need a steady resistance, for example to set bias current or to limit LED current. You cannot change its value after you make it.

Understanding Potentiometer Variable Resistor

What is a Potentiometer?

A potentiometer has three terminals: two ends of a resistive track and a wiper that moves. As you move the wiper, you change the resistance between terminals. You can use a potentiometer to split voltage or as a two-terminal variable resistor.

Types of Potentiometers

  • Rotary Potentiometer: You turn a knob to change resistance. You see this in volume controls.

  • Linear Potentiometer: You slide a wiper along a straight track. You find this in fader controls.

  • Adjustable Potentiometer: A small part on a PCB that you tune with a tool.

How a Potentiometer Works

Inside, there is a resistive track made of carbon or plastic. The wiper moves along this track. This changes how much track is in use. That changes resistance. You can hook it up to make a voltage divider or use two terminals as a rheostat.

Voltage Divider Circuit

In a voltage divider, the potentiometer splits the input voltage into two parts. When you move the wiper, you change the ratio of these voltages. You use this for sensor signals, adjustable power supplies, and more.

Potentiometer Variable Resistor vs. Fixed Resistor

Key Differences

Feature Variable Resistor (Potentiometer) Fixed Resistor
Resistance Adjustability You can change resistance by moving the wiper Resistance stays the same
Terminals Three (potentiometer) or two (rheostat) Two
Main Use Tuning levels, voltage dividing Steady resistance

Terminal Count

A potentiometer has three terminals: two ends of the track and a wiper. You can use it with two terminals as a variable resistor. A fixed resistor always has two terminals.

Function and Uses

  • Variable Potentiometer: Use it when you need to adjust levels, like volume or light dimming.

  • Fixed Resistor: Use it when you need a steady resistance, like in bias circuits or to limit current.

Applications of Potentiometer Variable Resistors

In Audio Equipment

A rotary potentiometer is good for volume and tone control. You get smooth changes in sound level.

In Lighting Control

You can use a variable resistor pot in a dimmer switch. Changing resistance changes the lamp current and the brightness.

In Measurement Devices

A linear potentiometer can measure position or displacement. As the wiper moves, the output voltage changes in proportion.

Conclusion

Choosing Between Potentiometer and Fixed Resistor

  • Pick a potentiometer variable resistor when you need to adjust resistance or use a voltage divider.

  • Pick a fixed resistor when you need a steady, known resistance.

Final Thoughts

Knowing the difference between a potentiometer vs variable resistor and a fixed resistor helps you build better circuits. Choose the one that fits your needs and your design will work more reliably.

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