Definition
A composite construction used in certain aircraft electrical components, particularly composition resistors and brush assemblies, in which finely ground carbon (an electrical conductor) is mixed with a non-conducting binder such as clay or a resin. The ratio of carbon to insulator determines the electrical resistance of the finished part: more carbon yields lower resistance, less carbon yields higher resistance.
Plain English
It's a mixture of carbon, which conducts electricity, and a material that does not conduct electricity. By changing how much of each is used, manufacturers can control how much the finished part resists the flow of electricity.
Context Anchor
Seen in aircraft electrical-system descriptions, especially when learning how older resistors or similar electrical parts are made.
Derivation
Carbon comes from a Latin word meaning coal or charcoal. Insulating comes from a word meaning to make separate or isolated. Together, the words point to the basic idea: one material can carry electricity, while the other helps separate and control that flow.
Why Pilots Care
A pilot does not normally repair these parts in flight, but understanding the phrase helps make aircraft electrical-system explanations less mysterious, especially when reading about resistance, overheating, or failed electrical components.
Analogy
Think of it like mixing salt into water. A little salt makes the water barely conductive; a lot of salt makes it conduct well. Adjusting the ratio of carbon to insulator works the same way for electrical resistance.
Intuition Check
Do not read this as carbon wrapped in insulation. In this context, the carbon and insulating material are mixed or combined so the part can control electrical flow.
Example Sentence 1
A composition resistor is made by molding carbon and an insulating material together, with the resistance value set by the proportions of each.
Example Sentence 2
Early aircraft voltmeters often contained a small disc of carbon and an insulating material to limit current to the meter movement.