Write an example in which the first law of thermodynamic is allowed but never be observed.

Explanation

For this an example is given below.
Nobody has ever seen a book lying on a table jumping to a height by itself. But such a thing would be possible if the principle of conservation of energy were the only restriction.
The table could cool spontaneously, converting some of its internal energy into an equal amount of mechanical energy of book, which would then hop to a height with potential energy equal to the mechanical energy it acquired. But this never happens.
Hence, principle which disallows many phenomena consistent with the first law of thermodynamics is known as the second law of thermodynamics.
The second law of thermodynamics gives a fundamental limitation to the efficiency of a heat engine and the coefficient of performance of a refrigerator.
The efficiency of a heat engine `eta=1=Q_2/Q_1`, can never be unity, mean never be 100%, because heat released `Q_2` to the cold reservoir (sink) can never be made zero. Means absorbed `Q_1` cannot converted completely into work.
For a refrigerator, the second law says that the coefficient of performance can and never be infinite. Because in `alpha=(DeltaQ)/W` , external work (W) can never be zero, suppose it zero then a is infinity but external work cannot be zero.
From this scientists Kelvin-Planck and Clausius gave the statements for second law of thermodynamics which are as follow :
(1) Kelvin-Planck Statement : No process is possible whose sole result is the absorption of heat from a reservoir and the complete conversion of the heat into work. For this schematic representation is given in below figure.

(ii) Clausius Statement : No process is possible whose sole result is the transfer of heat from a colder object to a hotter object. For this schematic representation is given in below figure.