Answer is:
Positive temperature coefficient
Explanation:
A positive temperature coefficient (PTC) refers to materials that experience an increase in electrical resistance when their temperature is raised. Materials which have useful engineering applications usually show a relatively rapid increase with temperature, i.e. a higher coefficient.
![What is the full form of the relay - PTC?](https://mcqfinder.in/uploads/images/objective-questions/mrac-set-1-refrigeration-direct-cool/mrac-set-1-refrigeration-direct-cool-id-4-e.jpg)