Electric heating elements convert electrical energy into heat energy through the principle of Joule heating

Electric heating elements convert electrical energy into heat energy through the principle of Joule heating. Almost any conductor will get hot when electricity flows through it, but the right combination of properties is required to make a good element.
Metal heating elements are typically made from a metal alloy such as nichrome (80% nickel, 20% chromium) in the form of coiled wire or flat ribbons. Other alloys such as molybdenum disilicide or silicon carbide are also used.
Resistance Wire
Resistance wires form the primary component of an electric heating element, restraining the flow of electricity that converts it into heat. It is critical that the resistance wire can withstand high temperatures, and is available in a range of alloys optimized for these demands - including nickel chrome, nickel chromium 80/20, nichrome, cupro nickel and iron nickel. Hyndman has the experience to advise which alloy is best suited to your application, as each type has specific properties such as electrical resistance, oxidation resistance and strength – all at elevated temperatures.
The size of the diameter of the resistance wire can also impact its performance. The wire's length is also a factor, since the longer it is, the more resistance it will have due to the fact that electrons within the wire are more likely to collide with ions, making it harder for an electric current to pass through.
When determining the resistance of a heating element, ohms law (voltage x current) provides a simple calculation. This enables the user to determine the current that is required for the task, and then use a power or wattage calculator to determine the amount of energy that the element needs.
A variety of applications require heating elements to be made from resistance wire, from household appliances such as toasters or handheld body massagers to industrial furnaces and electric stove burners. Sometimes these elements are encased in sheathed or tubular forms. Sheathed elements feature a fine coil of nichrome resistance heating alloy wire that is contained within a sheath made from another alloy such as copper or stainless steel. These sheathed elements can be incorporated into appliances as a straight rod or bent into a shape to span an area of an appliance such as an electric stove or oven. Alternatively, the sheath can be replaced with a ceramic material to further increase the efficiency of the element and reduce its operating costs.
Ceramic
Ceramic heaters transfer heat to their surroundings through conduction, convection, or radiant energy. Conductive ceramics such as silicon carbide transfer thermal energy between two objects in contact. In convective heaters like space heaters, the element carries thermal energy through the air and increases ambient temperatures. Radiative ceramics emit electromagnetic radiation that heats up objects through infrared wavelengths. Ceramic infrared heaters are very efficient and can be used to heat plastic materials, carbon-based materials and liquids. They can also be highly durable, withstanding vibration and harsh processes such as sintering or calcination.
PTC (positive temperature coefficient) ceramics are semi-conductive and have a negative composition-dependent threshold temperature above which their resistance quickly increases with the application of electrical current. When their threshold is reached, they automatically switch off avoiding overheating and damage. Ceramic heating elements made from these materials are a perfect choice for applications with high temperature gradients and short responses.
Ceramic infrared heaters are often designed to have a hollow construction which reduces the back surface temperature and increases watt density. They provide excellent energy efficiency since they only use the radiant energy that directly affects the product being heated. They are especially useful in applications such as sintering or calcination where the product itself is being heated rather than the air around it.
Tubular ceramic heaters consist of a resistance wire embedded within a tubular ceramic insulator. The insulator acts as a sheath, protecting the resistance wire from oxidation and making it safer and more effective. Tubular ceramic heating elements can be shaped into a variety of configurations depending on the application such as ring heaters, flat sheet heaters or rod-shaped heaters intended to go inside tubes. Ceramic insulators are usually sintered using simultaneous sintering and can be manufactured with built-in temperature sensors or output switching functions.