Engineering Thermodynamics
Which of the following is the correct statement of the second law of thermodynamics?

All of these
It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source
There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy
It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work

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Engineering Thermodynamics
The condition for the reversibility of a cycle is

All the processes, taking place in the cycle of operation, must be extremely slow
The working parts of the engine must be friction free
The pressure and temperature of the working substance must not differ, appreciably, from those of the surroundings at any stage in the process
All of these

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