Question

What are the limitations of the first law of thermodynamics?

Answer 1

Step1: First law of thermodynamics:

1. According to the first law of thermodynamics, the energy of the universe always remains constant.
2. It can be transferred between the system and the surroundings, but it cannot be generated or destroyed.
3. The law is primarily concerned with changes in energy states as a result of work and heat transmission. It redefines the concept of energy conservation.
4. The equation for the first law of thermodynamics is given as follows:

ΔU = q + W, where, $∆\mathrm{U}$ is the change in internal energy of the system, $\mathrm{q}$ is the algebraic sum of heat transfer between the system as well as surroundings, and, $\mathrm{W}$ is the work interaction of the system with its surroundings.

Step2: Limitations of the first law of thermodynamics:

1. According to the law, when a system goes through a thermodynamic process, it always maintains a specific energy balance. The first law, on the other hand, fails to account for the feasibility of the process or change of state.
2. It does not mention the direction of heat flow.
3. It says nothing about whether the process is spontaneous or not.
4. The process cannot be reversed. In practice, heat does not completely transform to work.