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What Is a Potentiometer?

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  • Originally Written By: Sanika B.
  • Revised By: A. Joseph
  • Edited By: Lucy Oppenheimer
  • Last Modified Date: 20 September 2014
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A potentiometer is a manually adjustable electrical resistor that uses three terminals. In many electrical devices, potentiometers are what establish the levels of output. For example, in a loudspeaker, a potentiometer is used to adjust the volume. In a television set, computer monitor or light dimmer, it can be used to control the brightness of the screen or light bulb.

How It Works

Potentiometers, sometimes called pots, are relatively simple devices. One terminal of the potentiometer is connected to a power source, and another is hooked up to a ground — a point with no voltage or resistance and which serves as a neutral reference point. The third terminal slides across a strip of resistive material. This resistive strip generally has a low resistance at one end, and its resistance gradually increases to a maximum resistance at the other end. The third terminal serves as the connection between the power source and ground, and it usually is operated by the user through the use of a knob or lever.

The user can adjust the position of the third terminal along the resistive strip to manually increase or decrease resistance. The amount of resistance determines how much current flows through a circuit. When used to regulate current, the potentiometer is limited by the maximum resistivity of the strip.

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Controlling Voltage

Potentiometers also can be used to control the potential difference, or voltage, across circuits. The setup involved in utilizing a potentiometer for this purpose is a little more complicated. It involves two circuits, with the first circuit consisting of a cell and a resistor. At one end, the cell is connected in series to the second circuit, and at the other end, it is connected to a potentiometer in parallel with the second circuit.

The potentiometer in this arrangement drops the voltage by an amount equal to the ratio between the resistance allowed by the position of the third terminal and the highest possible resistivity of the strip. In other words, if the knob controlling the resistance is positioned at the exact halfway point on the resistive strip, then the output voltage will drop by exactly 50 percent, no matter what the input voltage is. Unlike with electrical current regulation, voltage regulation is not limited by the maximum resistivity of the strip.

Rheostats

When only two of the three terminals are used, the potentiometer acts as a type of variable resistor called a rheostat. One end terminal is used, along with the sliding terminal. Rheostats typically are used to handle higher levels of current or higher voltage than potentiometers. For example, rheostats might be used to control motors in industrial machinery.

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Discuss this Article

anon355032
Post 43

Some places on the web kin of blur the line between a potentiometers and rotary encoders. Can you delineate the differences between the two?

agkyaw
Post 39

Can the potentiometer used to change polarity? Can it be used for reversing motors?

anon277624
Post 35

When does the resistance between terminal 1 and 2 vary the potentiometer's shaft?

anon244455
Post 30

How much supply is needed to control the voltage on a potentiometer?

anon157735
Post 28

Thanks for making the subject easy to understand.

anon155907
Post 27

what is the difference between linear and rotary potentiometers?

anon133272
Post 24

potentiometer is what kind of transducer?

anon122416
Post 23

Can I use a potentiometer for glycerine analysis?

Thanks, Kamran S.

anon91093
Post 21

Is there a color standard for a potentiometer? What is it, and what are the classification of the different colors?

anon82705
Post 19

what is the sensitivity of a potentiometer?

anon78603
Post 18

For anon300: If there are two terminals in a Potentiometer then it acts as rheostat.

anon76365
Post 17

what is the difference in rheostat and potentiometer?

anon70421
Post 16

what will be happen if there is no potentiometer in a circuit?

anon53703
Post 15

what is the value of that potentiometer? i mean is the maximum value when it is adjusted completely?

anon38706
Post 13

Its pretty f9 description, but please explain how to solve questions related to it in a better and easier way and understanding circuits given in complicated problems.

anon18384
Post 7

Twas a good description kind sir

anon16464
Post 6

Can a potentiometer be used to create an adjustable resistance, in place of a thermistor, to "fool" monitoring equipment?

anon12116
Post 3

Thank you for finally explaining in layman's terms what the heck a potentiometer is and how it is used! I have had to write up service reports from service technicians about potentionmeters and had no idea what they were talking about.

anon10521
Post 2

Thank you for the most straightforward description of a potentiometer I have come across so far.

It is incredible that you managed to convey the idea in words only.

Thanks again.

anon300
Post 1

Definition for potentiometer is fine and but one small request if you give working principle of that with diagram, then it could be very good.

Thanking you Sir,

Muralikrishna Sharma. S

[email address removed]

Moderator's reply: Any responses to the above question can be posted here.

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