What Are Carbon Composition Resistors and How Do They Work?

Resistors are common electronic components that are implemented in countless devices and systems, used for establishing electrical resistance within a circuit. Depending upon their type of resistor and application, such components may serve to reduce current flow, manage signal levels, bias active elements, divide voltages, and much more. Carbon composition resistors in particular are a common fixed resistor type, serving various devices and assemblies since the early 20th century. In this blog, we will discuss carbon composition resistors, ensuring that you have a well-developed understanding of their construction, functionalities, and applications.

For a standard carbon composition resistor, such parts may be constructed through the embedding of wire leads or metal end caps to a solid cylindrical resistor element. To protect the resistor, the body is often encapsulated within a coat of paint or plastic. Early variations often were designed without insulation added, and the lead wires were simply wrapped and soldered around the ends of the rod. In order to quickly and easily distinguish different values of carbon composition resistors, such components will regularly be color-coded with paint.

It is important to know that carbon composition resistor types are a form of fixed resistor, meaning that their resistance is unable to change regardless of adjustments to voltage or temperature. To form the resistive properties of such resistor types, a mixture of finely powdered carbon and an insulating material is produced and bound together with the use of a resin. To determine the resistance of a particular mixture, the ratio of the fill material and carbon may be adjusted. Carbon is considered to be an efficient conductor of power, thus a greater percentage of it within a mixture will result in a lower resistance capability for the component.

While the resistance values of carbon composition resistors are fixed based on their type and mixture, there are certain instances where resistance still may adjust. As the resistor continuously faces stress from over-voltage conditions, the value may slowly change over time. Internal moisture is also detrimental to the stability of such resistors, often posing the chance of creating non-reversible changes in resistance values due to soldering heat.

While carbon compositions were once an extremely popular choice for a variety of electronics, they have since lost their appeal for general use since the 1960s with the debut of other resistor types with better tolerances, voltage dependencies, and stress capabilities. Carbon composition resistors also face poor stability with time, often featuring tolerances of just 5%. Despite such shortcomings, carbon composition resistors are a non-inductive component, meaning that they can be advantageous for voltage pulse reduction and surge protection applications. Additionally, such resistors also have a higher capability to withstand overload conditions while having a smaller size.

Despite other resistor types replacing the carbon composition resistor for general use, there are still many variations available on the market. Ranging from under a single ohm to 22 megohms for their values, such resistors are often used within power supplies and welding controls, as well as vintage electronics for the means of upholding authenticity. If you find yourself in need of top quality carbon composition resistors for your various applications, let the experts at ASAP Parts Online help you secure all that you need with ease.

ASAP Parts Online is a premier supplier of aviation parts, electronics, IT hardware, and NSN components, providing customers competitive pricing and rapid lead-times on all that we carry. Take the time to explore our vast offerings, and our team of industry experts are always on standby 24/7x365 to assist customers through the purchasing process as necessary. If you would like to learn more about our offerings or are ready to begin procuring parts, give our team members a call or email at your earliest convenience and we would be more than happy to assist you as needed.

1. mary wilson
2. Posted on July 16, 2021
3. aviation

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