If you are asking what is a potentiometer, here is the short answer: a three-terminal variable resistor with a sliding contact. You turn or slide it to change resistance or to divide a voltage, as in volume knobs and dimmers.
This guide is part of a series on electronic components, written for people learning how common parts behave.
| Item | Value |
|---|---|
| Terminals on a potentiometer | Three |
| Power it is rarely used to control | More than a watt |
| Wiper travel on a single-turn pot | Approximately 270 degrees, or 3/4 of a full turn |
| Rotations on a multi-turn pot | Mostly 5, 10 or 20 |
| Setting change per angle on a multi-turn pot | Typically a tenth as much as a simple rotary pot |
These figures come from Wikipedia’s potentiometer article and EEPower’s resistor guide. Figures can change between sources and part datasheets, so check the source before you rely on them.
How a potentiometer works
A potentiometer, often shortened to “pot”, is a resistor you can adjust by hand. It consists of a resistive element, a sliding contact called the wiper, a terminal at each end of the element, a mechanism that moves the wiper and a housing, according to Wikipedia.
Two of the three terminals connect to the ends of the resistive element. The third connects to the wiper, and on panel potentiometers the wiper is usually the center terminal of three.
The idea rests on a simple rule: the resistance of an object is directly proportional to its length, as CUI Devices explains. Moving the wiper lengthens or shortens the path the current takes through the element, so the resistance on each side of the wiper changes.
A pot is also a passive component. The same CUI Devices page notes that it does not need a power supply or additional circuits to function.
The idea is old. The same page says the concept of the potentiometer was not proposed until 1841, and that the first working carbon potentiometer was invented by Thomas Edison in 1872.
Voltage divider or rheostat: two ways to wire it
A voltage divider is a network of resistors used to reduce a voltage by some factor, as the Phidgets potentiometer guide describes. Its worked example uses a 12 V supply with two resistors in series: a 5k and 10k pair gives 8 V at the midpoint, and swapping them gives 4 V.
A potentiometer is that same divider with a movable midpoint. To wire it this way you use all three pins:
- Connect one outer pin to ground.
- Connect the other outer pin to the supply voltage.
- Take the output from the middle pin, the wiper.
That sequence follows the Random Nerd Tutorials description. Turn the knob and the output voltage moves between the ground and supply levels.
Use only two terminals, one end and the wiper, and the part acts as a rheostat, or variable resistor, as Wikipedia states. A 10 kΩ pot wired this way gives anything from 0 Ω up to 10 kΩ, according to Random Nerd Tutorials.
One wiring habit is worth copying. EEPower says the best way to wire a pot as a rheostat is to connect the wiper and one end terminal together, which prevents infinite resistance if the wiper occasionally loses contact.
What are the main types of potentiometer?
Pots are grouped by how the wiper moves and by what they are for. The common families are:
- Rotary: the wiper moves along a circular path. A single-turn pot covers approximately 270 degrees, or 3/4 of a full turn, while multi-turn versions use mostly 5, 10 or 20 rotations for more precision, per EEPower.
- Slide (linear): the wiper moves in a straight track. Its slider position gives a visual indication of the setting, as in a graphic equalizer or the faders on a mixing console.
- Trimmer: a trimmer potentiometer is typically meant to be adjusted once or infrequently, per Wikipedia.
- Dual-gang: two potentiometers combined on the same shaft, enabling the parallel setting of two channels.
- Digital: controlled electronically, for example by up/down signals or serial protocols, instead of by hand.
Rotary and slide pots differ in how well they resist dirt. In a rotary pot the only point of ingress for contamination is the narrow space between the shaft and the housing. In a slider, contamination can enter anywhere along the slot, which makes sealing harder and compromises long-term reliability.
The resistive element also varies. Inexpensive pots often use graphite, and EEPower lists carbon composition, cermet, wirewound, conductive plastic and metal film among the materials used. Conductive plastic gives a very smooth feel and high resolution, while cermet is very stable with a low temperature coefficient.
Linear or logarithmic: what is taper?
The taper is the relationship between the wiper position and the resistance. The two most common forms are linear and logarithmic.
With a linear taper, a knob at the medium position gives an output voltage that is half of the voltage across the pot. Phidgets says linear tapers are often found in dials on analog equipment and as feedback devices on linear actuators or servo motors.
A logarithmic taper suits audio. Logarithmic tapers are primarily used in audio equipment since human perception of volume is logarithmic.
The Random Nerd Tutorials page adds a labelling tip: a linear pot is marked with a B and a logarithmic pot with an A. Treat that as a hint and confirm the taper in the datasheet of the exact part you buy.
Where are potentiometers used?
Pots turn a hand movement into an electrical level, so they show up wherever a person adjusts something. Wikipedia gives several examples:
- Volume controls on audio equipment.
- Speed control of fans.
- Position transducers, for example in a joystick.
- Position sensors in motion control systems, giving analog feedback to a controller.
Light dimmers are another case, though the pot does not carry the lamp current. As CUI Devices notes, a simple light dimmer uses a potentiometer to control a TRIAC, which varies the light brightness.
That points to the main limit. Potentiometers are rarely used to directly control significant power (more than a watt), since the power dissipated in the pot would be comparable to the power in the controlled load, per Wikipedia.
For a part that switches a circuit rather than adjusting it, the explainer on what is a relay is the natural comparison.
Choosing and looking after a potentiometer
Before you buy, settle a few points in this order:
- The maximum resistance, such as a 10 kΩ pot for a 10 kΩ range.
- The taper: linear for dials and feedback, logarithmic for audio volume.
- The movement: rotary, slide or trimmer, and single-turn or multi-turn.
- The element material, which affects feel, stability and wear.
- The power the pot will have to dissipate, which should stay small.
Good wiring matters as much as the part. Tie the wiper to an end terminal when using a pot as a rheostat, and keep dust and moisture away from the shaft opening or slider slot.
If you are building up a parts vocabulary, a good companion read is the explainer on what is a diode, another basic part you will meet on the same schematics.
Frequently asked questions
Is a potentiometer the same as a variable resistor?
Show answer
Nearly. A potentiometer has three terminals, and if only two are used, one end and the wiper, it acts as a variable resistor or rheostat.
What does the wiper do?
Show answer
The wiper is the sliding contact that moves along the resistive element. It connects to the third terminal and sets the resistance ratio, and therefore the output voltage when a reference voltage is applied across the end terminals.
Can a potentiometer control a motor or lamp directly?
Show answer
Rarely. Pots are rarely used to control more than a watt because the device must dissipate the power as heat. They usually adjust a small analog signal that another component, such as a TRIAC in a dimmer, uses to control the power.
What is a trimpot?
Show answer
A trimpot, or trimmer pot, is a trimmer potentiometer typically meant to be adjusted once or infrequently, often with a screwdriver, to fine-tune a signal.
