Question

According to second law of thermodynamics :

• A. all heat can be converted into work
• B. the efficiency of heat engine is always lesser than unity
• C. it is not possible to transfer heat energy from lower to higher temperature by itself
• D. when heat changes to other forms, energy is conserved

Answer 1

Answer: (B), (C)

the efficiency of heat engine is always lesser than unity
it is not possible to transfer heat energy from lower to higher temperature by itself

The second law of thermodynamics is governed by two statements.

(i) Kelvin-planck statement :- It states that, it is impossible for a device that operates in a cycle to receive heat from a single reservoir & produce net amount of work.

(ii) Clausis statement :- It states that, it is not possible to construct a device that operates in a cycle & produces no other effect other than transfer of heat from a body at higher temperature to a body at lower temperature.

The second law of thermodynamics also tells that for a feasible process, the efficiency of heat engine is always less than 1.