Resistors are electronic components that provide specific amounts of resistance to an electrical current in electronic circuits. Ceramic resistors can fall into many different classes of resistors. Which classes these are often depend on who is describing the resistor. To a layman or electrician, a ceramic resistor is often any resistor encased in ceramic. Engineers and technicians, on the other hand, define ceramic resistors as those that use ceramics to control a resistor’s resistive value.
Ceramics are a very common internal component of many different types of resistors. In a carbon film or resistive wire resistor, the resistive material adheres to the outside of a ceramic core, usually in the shape of a cylinder. These cores provide a non-conductive base to hold the conductive components of the resistor in place, and give the resistor its general shape and size.
While an excellent electrical insulator, ceramic is also an excellent heat conductor. This property of ceramic allows the cores of these resistors to endure low to moderate power electrical current throughput without overheating and becoming damaged. Ceramic’s use, however, is not limited to the internal components of resistors.
Because of its insulation and thermal properties, ceramic is used to externally insulate and provide even greater thermal endurance to some types of resistors. The most common of these types are resistors made of resistive wire spun around a ceramic core and then encased in a block or cylinder of ceramic material. Combining external ceramics with metals and internal ceramics allows these types of resistors to endure very high temperatures without damage.
The construction of a true ceramic resistor, often called a carbon composite resistor, is different from most other types, even though it also uses ceramics. Ceramic resistors are made of a combination of finely powdered carbon and ceramic material. These two powders combine in specific ratios to determine the final value of the resistor.
The higher ratio of carbon in the mix, the lower resistive valve the ceramic resistor will have. A higher ratio of ceramic material, on the other hand, will mean a higher resistive value of the resistor. Once the proper ratios are established, the mixture is compressed to create its shape and then kiln fired to set the ceramic. It is common for these types of resistors to have an external shell of pure ceramic material to serve as an external insulator.
True ceramic resistors are widely used in many different types of electronic circuits and devices. While these types of resistors can endure very high operation temperatures, they also create significant amounts of electrical noise. Due to this fact, a ceramic resistor seldom finds use in sensitive radio receivers or other devices particularly susceptible to interference.