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The potentiometer is a variable resistor which is used to control the resistance of electrical devices like motors. It consists of a dial or slider which has contacts on all its sides. When the slider is moved from one side to another, the intermediate contacts get closed and when it is released, all the contacts get opened and such movement allows adjustment in device resistance.
What is a Potentiometer?
The potentiometer consists of an input device and output device. The input device consists of the slider which is made up of conductive material and the output device consists of a dial or slider which can be placed anywhere in the circuit. When we apply force on a slider, then it gets moved away from its initial position towards the direction in which force is applied. Thus, when sliding action takes place, it leads to change in voltage across the resistance strip which ultimately leads to change in current across the resistor strip. Such movement creates a potential difference across the resistive strip at its ends and results in charge separation i.e movement of mobile charges constitutes electric current whereas missing charges constitute voltage across resistor strip.
Types of Potentiometers
Rotary Potentiometer
The potentiometer which has contact tracks on the dial is called a rotary potentiometer. It consists of a dial, resistive strip and a set of contacts. When the dial is rotated, the outer contacts of the resistive strip get connected to the inner contacts and thus resistance can be adjusted. Such action happens when sliding action is applied in clockwise direction and if we apply counter clockwise force, the current leads through all the contacts except the inner one.
Linear Potentiometer
The potentiometers which have contact tracks on a linear slider are known as linear potentiometers. Here, the slider moves linearly along a resistive strip and hence when linear motion takes place then it changes resistance in three steps i.e. linear resistance of the slider. This leads to the change in circuit behaviour and when it comes to the purpose of the potentiometer, it helps to control devices which require a change in voltage by adjusting the current. It consists of one resistor and two resistive strips. When linear motion takes place along the slider then current passes through outer solenoids as well as inner solenoid and such changes in circuit get reflected by change in resistance. Therefore, we say that the linear potentiometer also is known as ‘Two-Resistor Potentiometer’.
Working Principle
When we applied sliding force on sliders of potentiometers, then there is a significant change in voltage across them. This change is not continuous rather it is of short duration and is of the order of milliseconds. In order to understand this concept, we apply force on the slider then it moves towards the direction of force and when we release the force then the slider comes back to initial position by applying backward force. This backward motion takes place in such a way that it reaches to the original position from its current position with a certain velocity. Such movement creates a certain potential difference across the resistive strip at its ends and results in charge separation which i.e. movement of mobile charges constitutes electric current whereas missing charges constitute voltage across resistor strip. Following is the derivation of used to explain the potentiometer working principle:
V=IR
(Ohm’s law)
Where,
I: current
R: total resistance
V: voltage
Significance of Potentiometer
It is used to sense the changes in light, temperature, chemicals and other mechanical conditions. The construction of potentiometer along with its working principle have been described in detail above. Also, it is an output device which helps in detecting subtle changes of voltage over time. Hence, potentiometer is an effective component and can be used as a component in a variety of electronic circuits like amplifiers and other electronic devices.
Functions of Potentiometer
1) They are used in recording devices like record players and other electronic instruments.
2) Potentiometer is used in voltage scaling.
3) It is used in generating sound when it gets connected to the motor of a record player.
4) It can be used as a component in circuits which involves intensifying the current which ultimately leads to amplification of voltage.
5) It can be applied for controlling an array or number of electric circuits and hence potentiometer works as a switch.
6) They are also used as sensor devices for detecting light, temperature, chemicals and other mechanical conditions and such sensors are also known as photovoltaic cells.
Potentiometer Applications
In Audio Circuits
They are used in various kinds of record players and other stereo equipment like phonograph, tape deck etc.
In Laboratory Instruments
They are used in laboratory instruments to measure voltage, current, resistance and other such electrical parameters.
For Measuring Light Intensity
They are used to detect light intensity and hence they are also known as photovoltaic cells. These types of cells convert sunlight energy into electrical energy. They work as an efficient light-sensor which provides the required amount of current for sensing the intensity of light emanating from a lamp or surface for a particular period of time.
Conclusion
In the present article, we have discussed the working principle and significance of potentiometers. Also, we have provided several examples of potentiometers from all the possible applications of potentiometer. Potentiometers are very much useful for sensing light or temperature changes etc. Hence, we can say that potentiometer is an essential component for measuring electrical parameters like voltage and current etc and in such a case it becomes a device for converting between electrical quantities.
Now that you have read about what a potentiometer is, it is important to know how to use them. A potentiometer is essentially a variable resistor that varies its resistance depending on how much voltage you put across it (the more voltage the more resistance).
