Question 8: Write the limitations of the First Law of Thermodynamics.

ANSWER

Limitations of the First Law of Thermodynamics:

1. First Law of Thermodynamics is the law of conservation of energy. It tells us one form of energy can be converted to another form of energy and the total sum of energies before and after the process remains constant. However, it does not give any information about the direction of the process. For example, a hot cup of tea cools off when kept in the cooler room temperature. However, heat does not transfer from the cold room to hot cup of tea. Hence it is one of the limitations of the law that it doesn’t inform us about the direction of the process.
2. It does not tell us whether a process is feasible or not, that is, whether it will take place or not. Water flows down the hill and potential energy is converted into kinetic energy. The reverse does not occur in the nature though it is not wrong according to the First Law of Thermodynamics that water go up hill and the kinetic energy converts to potential energy.
3. The law does not tell us what percent or part of energy will be converted from one form to another in a particular process. Heat can be converted to an equivalent amount of work but work cannot be converted to an equivalent amount of heat. First Law is silent on this aspect of conversion.

The Second Law of Thermodynamics successfully overcomes these limitations. It tells us about the feasibility (possibility) of a process and the direction in which it will occur.