Kelvin–Planck Statement – What It Addresses Kelvin–Planck's statement of the second law deals with the impossibility of complete conversion of heat into work in a cyclic engine (limits on conversion of heat to work).

Introduction / Context:
Several equivalent statements express the second law. The Kelvin–Planck form addresses heat engines and the fundamental limit that no cyclic device can convert all absorbed heat into work when operating with a single heat reservoir.

Given Data / Assumptions:

• Cyclic heat engine exchanging heat with thermal reservoirs.
• Single reservoir assumption for the impossibility statement.
• Macroscopic, classical thermodynamics framework.

Concept / Approach:

Kelvin–Planck statement: It is impossible for a device that operates on a cycle to receive heat from a single reservoir and produce an equivalent amount of work with no other effect. Thus, full conversion of heat to work is prohibited; some heat must be rejected to a lower-temperature sink.

Step-by-Step Solution:

Verification / Alternative check:

Equivalence to the Clausius statement can be shown via logical contradiction: violating one enables violation of the other and vice versa.

Why Other Options Are Wrong:

Conservation of work/heat are First-law ideas. Conversion of work into heat is always possible (e.g., friction), not prohibited by the second law. Equivalence notes the mechanical equivalent of heat but not the second-law limitation.

Common Pitfalls:

Confusing efficiency limits with First-law balances; forgetting that multiple reservoirs are necessary for heat engine operation.

Final Answer:

conversion of heat into work