GITAM, Department of Engineering Physics
Heat and Work
Heat is a form of energy which flows from one body to another on account of temperature difference between them. Thus the flow of heat is a non-mechanical energy transfer.
But if a system loses energy by other methods, generally, by working against external mechanical forces, it is said to do work. Thus work is the transfer of energy without a temperature difference.
- Heat and work are both transient phenomenon. Systems do not possess heat or work.
- When a system undergoes a change, heat is transferred or work is done.
- Heat and work are boundary phenomenon. They are observed at the boundary of the system.
- Heat and work represent the energy crossing the boundary of the system.
- Heat and work are path functions and hence they are exact differentials.
- It is customary to represent work done by the system as +ve while work done on the system as –ve. Similarly heat flowing into the system as +ve and heat flowing out of the system as –ve.