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    A potentiometer, called pot for short, is an electrical component that acts as a variable voltage divider. They usually have three terminals, one of which is connected to a moving center contact. A potentiometer with two terminals is a variable resistor, called a rheostat. Potentiometers come in many forms including rotaries, trimmers, sliders.

    Potentiometer is also the term for an old instrument that measured an unknown voltage after being calibrated with a known voltage. These have been replaced by multimeters today.

    Potentiometer Types

    Rotary potentiometers have a semi-circular contact made of a resistive material, such as graphite or wire. Each end of the contact is connected to a terminal, and a voltage is applied across the terminals. The shaft is connected to another contact which moves across the surface of the graphite contract, and this contact is connected to the third terminal. The voltage at this output terminal depends on the position of the shaft, provided that the voltage across the two input terminals remains steady.

    Trimmer potentiometers, called trimpots for short, are small rotary versions used on circuit boards to fine tune the voltage levels in a circuit. They are typically set at the factory and rarely adjusted again. They are adjusted using a screwdriver because they do not have a shaft or slider.

    Sliding potentiometers, also called faders, have a straight section of resistive material between two terminals on one side, and a contact that move along the other side connected to the third terminal.

    Digital potentiometers are software programs that use a computer to make minor voltage adjustments without the need for mechanical parts. They are commonly used in music production which would otherwise required a lot of regular potentiometers.

    Potentiometers can have either a linear or logarithmic relationship between their position and resistance, depending on the construction of the resistive element. A logarithmic relationship is obtained by tapering the resistive materials, while a linear relationship requires a constant width.

    Potentiometer Applications

    Potentiometers are compact devices used for adjusting the voltage at specific points in a circuit. They are most commonly used to control the audio output of radios and televisions. Volume, bass, treble, and speaker balance are all adjusted with potentiometers. They also control the brightness, contrast, and color balance in televisions. Rheostats are used in light dimmers to control the current reaching the lights.

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    1. Raphael

      13 April, 2012 at 11:01 pm

      Are potentiometers and rheostats always so small or do they come in all different sizes for higher currents? For example, are there rheostats that can control 24 VDC motors that run on 30-40 amp circuits?


    2. Tajinder

      16 March, 2011 at 5:24 am

      Main difference between both of them is Rheostat has two legs and Potentiometer has three leg, cant understand the concept why Potentiometer has three legs, whats it use for.


      • memenode

        16 March, 2011 at 3:38 pm

        The third leg is wired to a wiper that selects a specific voltage from the voltage source (wired with the other two legs).

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