Heat and Thermodynamics

Why you feel yourself warm at a time when you come out of a cold room when air conditioner is switched On ? Why you feel hot when you touch a cup of tea/coffee ? Why your hands feel warmer when you rub your hands continuously ?

Well, the answer is that is an energy which is transfered from warmer body (cup of tea) to the colder one (your hands) due to the difference of temperature between them. This energy is called HEAT.

So heat is defined as:

Definition: 

The energy which transfers from hotter body to colder one till thermal equilibrium is established; due to the difference of temperature between them.

Unit: In SI system, heat is measured in Joules (J). However, in CGS system, it is measured in calorie (cal). In FPS system, it is measured in BTU (British thermal unit).

NOTE: 1 cal= 4.2 J

             1 BTU= 252 cal= 1055 J