To find:
2nd law of thermodynamics and its example.
Explanation:
There are more than one statement for the second law;
Kelvin-Planck statement:
No process is possible whose sole result is to completely convert the heat supplied from the source into useful work.
This means it is impossible to convert 100% of heat supplied into work by any device.
Clausius statement:
No process is possible whose sole result is the transfer of heat from a colder object to a hotter object.
The above two statements are equivalent.
Example for the 2nd law:
When two objects which are at different temperatures are kept in contact, the heat will always flow from the hotter object to the colder object unless the work is done to supply the heat from the colder object to the hotter object.
