Question

The second law of thermodynamics explains which of the following?

Answer 1

Answer:

The correct option is;

Why car engines are not perfectly efficient

Explanation:

The Second Law of Thermodynamics states that the total entropy, S, of a system combined with the entropy of its surrounding cannot be decreased, such that for an irreversible process, the entropy always increases and $S_f$ > $S_i$, while for a reversible process the entropy is constant and $S_f = S_i$

The entropy is a measure of the amount of useful work obtainable from heat (or thermal) energy

A system with a low entropy has high amounts of heat energy capable of doing work while a high entropy system can produce only a small amount of useful work from the available thermal energy

In car engines, as the parts start to move, the entropy of the system increases alongside the generated heat lost to the environment, the amount of heat available for doing work reduces and therefore, the entropy increases further and the ratio of work obtainable from a given input of heat energy reduces and therefore, the car engine is not perfectly efficient.