Potentiometer Working: Explained With Types, Measurement, Applications

One of the most common basic components in an electric circuit are resistors. These resistors come in a variety of shapes and sizes and are mostly used to regulate current flow by moderating resistance from the circuit. The potentiometer is the most common of the numerous linear and non-linear variable resistors available. A potentiometer is used to measure voltage or potential difference sn unknown voltage with a known voltage. This Physics article will discuss the potentiometer working, types of potentiometer and its applications.

Before that, let’s get more insight into the potentiometer.

What is a Potentiometer?

The term “potentiometer” is derived from the words potential difference and metering and dates back to the early days of electronic development. It was assumed at the time, that modifying big wire-wound resistive coils was determined by detecting a predetermined amount of potential difference.

Potentiometers are three-terminal variable resistors with resistance used to control the flow of current. Because of the resistance of the potentiometer, a large amount of current is restricted as the temperature rises, and only a small amount of current is allowed to pass through the circuit.

Potentiometer Working

To understand the working of a potentiometer, it is essential to learn about its parts and construction.

Construction of Potentiometer

The potentiometer is made up of a long resistive wire L made of magnum or constantan and a known EMF V. This voltage is referred to as driver cell voltage. As shown below, the two ends of the resistive wire L are connected to the battery terminals; this is assumed to be the primary circuit arrangement. At one end of the primary circuit is one of the terminals of another cell (whose EMF E is to be measured). A galvanometer G connects the other end of the cell terminal to any point on the resistive wire. The secondary circuit is formed by this arrangement. The potentiometer configuration is shown below:

Potentiometer Diagram

Working Principle

The principle of operation of a potentiometer is based on the notion that the drop in potential across any piece of a wire is exactly proportional to the wire’s length. Let’s assume the wire has a uniform cross-sectional area and a constant current flowing through it. Whenever there is no potential difference between any two nodes, no electric current flows. The sensitivity of potentiometer can be increased by increasing the length of the potentiometer. 

Types of Potentiometers

Potentiometers are classified into three types: linear potentiometers, rotary potentiometers, and digital potentiometers. Each one has been tailored to meet specific requirements. However, rotary POTs are the most common type of potentiometer.

Rotary Potentiometer

Rotary-type potentiometers are primarily used to provide variable supply voltage to a portion of electronic and electrical circuits. A popular example of a rotary potentiometer is the volume controller of a radio transistor, where the rotary knob controls the supply to the amplifier.

Rotary potentiometers are classified as single-turn pots, multi-turn pots, concentric pots, dual-gang pots, and servo pots.

Linear Potentiometer

Linear potentiometer is similar to the rotary potentiometer, but instead of rotary movement, the sliding contact on the resistor is moved linearly. Two ends of a straight resistor have been connected across the source voltage in this case. A sliding contact can be slid on the resistor via a track that is attached to the resistor. The terminal connected towards the sliding is connected to one end of the output circuit, and one of the resistor terminals is connected to the other end. Linear pots come in a variety of styles, including motorised faders, multi-turn slides, slide pots, and dual-slide pots.

Digital Potentiometer

Digital potentiometers have three terminals: two fixed end terminals and one wiper terminal for varying the output voltage. Digital potentiometers are used for a variety of purposes, including system calibration, adjusting offset voltage, tuning filters, controlling screen brightness, and controlling sound volume. In terms of construction, digital potentiometers differ from other types of potentiometers. This resistive digital to analog converter is digitally controlled (unlike linear and rotary that were manually controlled). It emulates the analog functions of the potentiometer to achieve the desired result.

Difference between Potentiometer and Voltmeter

The difference between potentiometer and voltmeter are discussed below.

Potentiometer	Voltmeter
A potentiometer precisely measures the emf of a cell.	A voltmeter approximates the emf of a cell.
While measuring current, the potentiometer does not draw any current from a known emf source.	While measuring current, voltmeters draw current from a known emf source.
When measuring emf, the potentiometer’s resistance becomes infinite.	When measuring emf, the voltmeter’s resistance rises dramatically but remains measurable.
The potentiometer has a high sensitivity.	The voltmeter has a low sensitivity.
It uses the null deflection method.	It employs the deflection method.

Measurement of Voltage with Potentiometer

The principle of measuring voltage across such a branch of a circuit using a potentiometer is also direct. First, we must adjust the rheostat to change the current flowing through the resistor such that it causes a specific voltage drop per unit length of the resistor.

By connecting one end of the branch to the beginning of the resistor and the other end to the resistor’s sliding contact via a galvanometer. And then by sliding the resistor’s sliding contact until the galvanometer shows zero deflection. When the galvanometer reaches zero, the voltage across the branch of the circuit can be measured.

Applications of Potentiometer

Some main applications of a potentiometer are as follows.

• In the electronic circuit, the potentiometer serves as a voltage divider.
• The potentiometer is employed in radio and television (TV) receivers to control volume, tone, and linearity.
• Potentiometers are found in medical equipment.
• It’s found in woodworking machines.
• It’s found in injection moulding machines.
• Potentiometers are extensively used as user controls and can be used to control a wide range of equipment functions.

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