Editing Thermistor (section)

===PTC===
* As current-limiting devices for circuit protection, as replacements for fuses. Current through the device causes a small amount of resistive heating. If the current is large enough to generate heat more quickly than the device can lose it to its surroundings, the device heats up, causing its resistance to increase. This creates a self-reinforcing effect that drives the resistance upwards, therefore limiting the current.
* As timers in the [[degauss|degaussing coil]] circuit of most CRT displays. When the display unit is initially switched on, current flows through the thermistor and degaussing coil. The coil and thermistor are intentionally sized so that the current flow will heat the thermistor to the point that the degaussing coil shuts off in under a second. For effective degaussing, it is necessary that the magnitude of the alternating magnetic field produced by the degaussing coil decreases smoothly and continuously, rather than sharply switching off or decreasing in steps; the PTC thermistor accomplishes this naturally as it heats up. A degaussing circuit using a PTC thermistor is simple, reliable (for its simplicity), and inexpensive.
* As heaters, in the automotive industry, to provide cabin heating (in addition to heating provided by a heat pump or the waste heat of an internal combustion engine), or to heat diesel fuel in cold conditions before engine injection.
* In temperature-compensated voltage-controlled oscillators in [[synthesizer]]s.<ref>{{cite web|url=http://www.oldcrows.net/~patchell/synthmodules/vco.html|title=Temperature Compensated VCO|first=Jim|last=Patchell|website=www.oldcrows.net}}</ref>
* In [[lithium battery]] protection circuits.<ref>Patent CN 1273423A (China)</ref>
* In an electrically actuated [[wax motor]] to provide the heat necessary to expand the wax.
* Many electric motors and dry type power transformers incorporate PTC thermistors in their windings. When used in conjunction with a monitoring relay they provide overtemperature protection to prevent insulation damage. The equipment manufacturer selects a thermistor with a highly non-linear response curve where resistance increases dramatically at the maximum allowable winding temperature, causing the relay to operate.
*To prevent [[Thermal runaway#Electrical engineering|thermal runaway]] in electronic circuits. Many electronic devices, for example [[Bipolar junction transistors#Vulnerabilities|bipolar transistors]], draw more power as they get hotter. Commonly, such circuits contain ordinary resistors to limit the current available and prevent the device from overheating. However, in some applications, PTC thermistors allow better performance than resistors.
*To prevent [[current hogging]] in electronic circuits. Current hogging can occur when electronic devices are connected in parallel. In severe cases, current hogging can cause cascading failure of all the devices. A PTC thermistor attached in series with each device can assure the current is divided reasonably evenly between the devices.  
*In crystal oscillators for temperature compensation, medical equipment temperature control, and industrial automation, silicon PTC thermistors display a nearly linear positive temperature coefficient (0.7%/°C). A linearization resistor can be added if further linearization is needed.<ref>{{Cite web|url=https://www.ei-sensor.com/thermistors/ed35s-ptc-thermistors/|title = ED35S PTC Thermistors}}</ref>