What describes a heating device that consists of a nickel-chrome spiral resistor embedded in refractory material?

The heating device described consists of a nickel-chrome spiral resistor embedded in refractory material, which directly correlates with the definition of a metal sheath element. This type of heater is designed to withstand high temperatures and efficiently transfer heat to the surrounding material. The nickel-chrome alloy is chosen for its excellent electrical resistance and durability, allowing it to generate significant heat when an electric current passes through it. The refractory material around the resistor helps to protect the element and enhances heat retention, making this combination effective for various heating applications.

In contrast, a ceramic heater typically uses ceramic materials to generate and radiate heat, while a plastic heating device would not possess the durability or heat resistance of metal components. An infrared heater operates differently by emitting infrared radiation to warm objects directly, rather than relying on a resistor embedded in refractory material. Therefore, the specifics of the method and materials used in the heating device clearly identify it as a metal sheath element.