Positive temperature coefficient or PTCs can be defined as the apparent attribute of metal to display an increase in its resistance quality towards electric current when they are exposed to gradually increasing high temperatures.

In the field of engineering, conductors and insulators have several methods of applications. The most significant characteristic among elements and alloys due to which they are made use of in form of conductors or insulators is their resistance towards the electric current. This concept in scientific language is known as the temperature coefficient. In simplest of terms, temperature coefficient can be explained as the ability of any metal(s) to increase, decrease or maintain their resistance towards electric current when they are exposed to gradually increasing high temperatures. In pure metals such as gold or silver, the temperature coefficient is positive meaning they increase their resistance with an increase in temperature which is known as Positive Temperature Coefficient. Similarly, the Negative Temperature Coefficient occurs when the material showcases a decline in its resisting attributes with increasing temperatures. Temperature coefficient in most metal alloys such as brass or bronze display almost no change in their resistance as they as exposed to rising temperatures which is known as Zero Temperature Coefficient.

 The theoretical concept of temperature coefficient (positive, negative and constant) are most commonly put in practice in the process of building circuits. Material with Positive Temperature Coefficient is mostly utilized as conductors while materials with Negative Temperature Coefficient are mainly used for building insulators.