Carbon Resistor

What Is a Carbon Resistor? Definition, Parts, Working Principle, Applications


A carbon resistor is a fixed form of a resistor. The resistor has been in existence for over a hundred years. In the beginning, the resistors that were produced were without coating. The only type of available resistors was that of wire wound and carbon composition. The resistor is made of fine carbon fragments, with a binder in a cylindrical shape and baked with terminal lead at the opposite end are known as carbon resistors.

These carbon composition resistors are widely utilized in the electrical circuits, and the majority of the resistors are made of metal or carbon films over a ceramic carrier. The most significant advantage of the carbon resistor is its ability to withhold high energy pulses. The carbon resistors' entire body conducts the energy for the electric current flowing through them. The carbon resistor is available in different physical sizes having a power dissipation limit from 1 watt down to 1/8 watt. 

What is a Carbon Resistor?

Carbon Resistor Definition - Many of the materials like nichrome, brass, platinum, and tungsten, which are metal, and alloys are used to produce the resistance. But most of these metals have low electrical resistance compared to carbon resistors, as it makes it difficult to produce high resistance without making the resistor bulky. It is already known that resistance is directly proportional to the product of the length and resistivity of the resistor. As the carbon resistor can produce a high accuracy value of resistance, it is usually used to calibrate the resistance. 

Carbon resistors are cheap, compact, and they can be directly added to the circuit boards like that of a tablet, mobile phones, and laptop processors. Due to all these practical purposes, they are more preferred as the metal wires are more expensive to produce compared to the carbon, which is available in large quantities. Within the practical requirement, the resistance is reproduced by the carbon resistors.  

Parts of a Carbon Resistor 

Construction of Carbon Resistor

Thought a variety of materials could construct carbon resistor, some parts of the carbon resistor are mentioned below

  • Ceramic core

  • Carbon film

  • Nickel Cap

  • Lead

  • Copper lead

  • Protective epoxy layer

The internal structure of the carbon resistor is shown in the below diagram. 

The carbon resistors are manufactured by using the deposition process. In this process, the carbon film is deposited upon the ceramic body of the resistor. The carbon film restricts the current flow, and as a result, it is an imperative part of the resistor. At a high temperature of 1000°C, hydrocarbons like methane or benzene are cracked. The ceramic mold acts as an insulator to the high temperature or the electricity, and pure graphite (carbon) is used for distribution on the ceramic body. The presence of the carbon film makes the resistor withstand the electricity without any damage. The diagram below is the schematic construction of a carbon resistor.

In the above figure, it is observed that the carbon film is in helical shape as it helps to accurately resist this carbon resistor. It also helps the effectiveness of the resistor with the decrease in the width and increase in the length.

As mentioned earlier, resistance is directly proportional to the distance; the value of the resistor can also be altered by increasing or decreasing the length of the spiral carbon film. For the protection of the resistor, an epoxy coating is also provided. The end portion, as shown in the diagram, is made up of metal, and the connecting leads are made up of copper, which are joined to the metallic ends.

How Does Carbon Resistor Work?

When people construct an electric or electronic circuit for a particular job, they need to induce the precise amount of resistance in the circuit board. It is achieved by adding the tiny components called the carbon resistor. These components are a little package of resistance that is wired into the circuit so that a precise amount can reduce the flow of current. 

What is the Symbol of Carbon Resistor?

In most of the electrical and electronic circuit diagrams, the most frequently used symbol is that of a zig-zag line for a resistor with the value of its resistance denoted by the Ohms. Fixed resistors usually have only one value of the resistance. Still, variable resistors can be provided with an infinite number of resistances, which may vary from zero to their maximum value.

Carbon Resistor Symbol

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FAQ (Frequently Asked Questions)

1. What are the Uses of Carbon Resistors?

The uses of carbon resistor are given below:

As the carbon resistor is suitable to withstand high energy pulses considering its relatively small size, we are able to be utilized in various applications used in day-to-day life.

The operating temperature of the resistor can be up to 350°C and a voltage up to 15KV. A carbon resistor is applied to the power supplies of X-rays, radar systems, and laser.

It is also used in medical defibrillators and other sensitive measurement equipment that is attached to the patient and which needs to be protected against high energy pulse.

2. What are the Advantages/Disadvantages of carbon resistors?

  • One of the most significant benefits of the Carbon resistor is that it can withstand high energy pulses. 

  • The entire body of the carbon resistor conducts the energy when the current flows through it.

  • The carbon resistors are cheaper to make and can have a higher resistance than that of wire-wound resistors.

  • The massive drawback of a carbon resistor is its high negative coefficient of resistance which makes the resistance change quickly with the difference in the temperature. As the temperature increases, the resistance decreases for the resistor.

3. What is the Application of a Thermistor? 

The conversion of electric voltage from temperature is achieved by using the thermistor.

4. What is the Value of Tolerance of Gold Color Resistance?

The value of tolerance is 5% of the gold color resistor.

5. What are the Uses of Rheostat?

The uses of rheostat are it can be used as a variable resistor as well as a potential divider.

6. What is the Tolerance Value of the Silver Strip? 

The value of tolerance is ±10% for a silver strip resistor.