What is Heat?
Heat is the energy transfer without transfer of mass across the boundary of the system because of the temperature difference between the system and surrounding. The heat is transferred across the boundary from system at high temperature to a system at lower temperature. The heat given to a system is taken as positive and heat getting from the system is taken as negative. The heat transfer can be identified only when it crosses the boundary.
Heat can transfer in three ways, namely
The way in which the heat is transferred from one molecule to another molecule within in a medium either solid or liquid or gas for which there should be direct physical contact between the molecules.
The way in which the heat is transferred between solid molecule and fluid molecule, the fluid molecule may be liquid molecule or gas molecule as both liquid and gas are fluids. But in conduction the heat is transferred between molecules of same medium either solid or liquid or gas where as in convection the heat is transferred between different medium’s molecules (solid and fluid).
It is heat transfer from one molecule to another molecule without any medium between them. It is the electromagnetic wave phenomenon i.e heat is transferred through electromagnetic waves. Any body above o Kelvin can emit electromagnetic waves. Example : we know that space contains no medium, it is vacuum, but the heat from the sun reaches earth through electromagnetic waves. This known as radiation.
What is Temperature?
It is the physical quantity which indicates the degree of hotness or level of heat intensity of the body. It’s unit is Celsius or Fahrenheit or Rankine.