The name self-regulating heater comes from the tendency of such heating elements to maintain a constant temperature when supplied by a given voltage.
[1] Some PTC heating elements are designed to have a sharp change in resistance at a particular temperature.
These elements are called self-regulating because they tend to maintain that temperature even if the applied voltage[1] or heat load[2] changes.
In some applications, this self-regulating characteristic allows PTC heaters to be used without thermostats or overtemperature protection circuits.
For example, a PTC heating element with a sharp change in resistance at a particular temperature can be fitted with a constant voltage source and a variable-speed fan.
The temperature such a material tends to hold can be adjusted by changing the voltage applied.
Conventional heating elements are constrained to be long and thin (often coiled to save space) to prevent current hogging.
[citation needed] Positive temperature coefficient heating elements can be made of several materials.
Heating elements of complex shape can be easily manufactured using printing techniques.
Since PTC heating elements are a kind of thermistor, they share the same principles of operation.
In some applications where the heater is used only in a narrow temperature range, a simple linear equation may be adequate.