What is a Variable Resistor?

A variable resistor, commonly known as a potentiometer or rheostat, is an electronic component that allows you to adjust the amount of resistance in a circuit manually. Unlike fixed resistors that have a static value, variable resistors feature a sliding or rotating contact called a "wiper." By moving the wiper along a resistive element, you can vary the voltage or current flowing through the device.

How to Use This Online Calculator

This Variable Resistor Calculator is designed for linear potentiometers. To find your values, follow these steps:

1. Enter Total Resistance: Input the maximum resistance value printed on your component (e.g., 10k, 50k, or 100k).
2. Select Unit: Choose between Ohms (Ω), Kiloohms (kΩ), or Megaohms (MΩ).
3. Adjust Wiper Position: Use the slider to represent the physical position of the knob or slider on your hardware.
4. Read the Results: The tool instantly calculates the resistance between the first terminal and the wiper (R1), and the wiper and the third terminal (R2).

Linear vs. Logarithmic Tapers

It is important to note that this calculator assumes a linear taper. In a linear potentiometer, the resistance changes in direct proportion to the wiper position. For example, at 50% rotation, the resistance is exactly half of the total. In contrast, logarithmic (or audio) tapers change resistance on a curve to mimic human hearing, making them more common in volume controls.

Frequently Asked Questions

Q: What is the difference between a potentiometer and a rheostat?
A: A potentiometer uses all three terminals to act as a voltage divider. A rheostat uses only two terminals (one end and the wiper) to control current flow in a circuit.

Q: Can I use this for high-power circuits?
A: Most standard variable resistors are designed for low-power signal adjustment. For high-power applications, ensure your component has a sufficient wattage rating to prevent overheating.