Choose Kelvin-Plank statement among the following

Kelvin-Plank statement: It is impossible for a heat engine to produce net work in a complete cycle if it exchanges heat only with bodies at a single fixed temperature.

For heat engine to operate, the working fluid has to exchange heat with a heat sink as well with the heat source.

If QL = 0, then 

Therefore, the second law claims that no heat engine can be 100% efficient.

So, W = Q (is impossible)

There will be always some heat loss to the surrounding.

W = QH – QL (is possible)

As (QH – QL) ≥ 0 so Wcycle ≥ 0

Clausius statement of Second law of Thermodynamics:

It is impossible to construct a system which will operate in a cycle, transfers heat from the low-temperature reservoir (or object) to the high-temperature reservoir (or object) without any external effect or work interaction with the surrounding.

• It is impossible to construct a device that operates on a cycle and produces no effect other than the transfer of heat from a lower temperature body to a higher temperature body.
• The Clausius statement is related to refrigerators as well as heat pumps.