First Law of Thermodynamics
First law of thermodynamics is also called the energy conservation principle according to which energy can neither be created nor be destroyed but it can only transffered from one form to another form of energy. The basic meaning of the 1st law of thermodynamics is that the energy of the universe is an isolated system.
Let us consider an isolated system and put some amount of heat (q) in it. According to first law of thermodynamics, the heat energy can not be lost but it must remain in the system as internal energy doing mechanical work. So,
Heat absorbed = Increase in internal energy + Work done by the system.
or, Increase in internal energy = Heat absorbed − Work done by the system.
Let 'q' be the quantity of heat absorbed, 'W' is the amount of work done, dE is change in internal energy. then-
dE = q − W
or, q = dE + W
For isolated system:
q = 0
so, dE = − W
For cyclic system:
dE = 0
so, q = W
For large change:
Q = dE + W
Limitations of the First Law of Thermodynamics
Some main limitations of the first law of thermodynamics are discussed below:
- It does not indicate the direction of heat flow
- It does not determine the feasibility of a process
- It does not explain irreversible processes
- It does not account for the efficiency of energy conversion
- It does not consider the quality of energy
Second Law of Thermodynamics and Its Limitations
Third Law of Thermodynamics and Its Limitations
