Joule: the mechanical equivalent of heat

What changed

Compared mechanical work with heat produced by friction in water, mercury and cast iron, establishing an experimental conversion relationship.

Scientific scope

Compared mechanical work with heat produced by friction in water, mercury and cast iron, establishing an experimental conversion relationship. Scope limitation: The paper uses historical units, temperature ranges and corrections. Its measured value is not a modern exact constant, and this record does not assign the entire development of energy conservation to one person.

Evidence

Assessment uses the catalogue-linked source evidence for the stated contribution. The paper uses historical units, temperature ranges and corrections. Its measured value is not a modern exact constant, and this record does not assign the entire development of energy conservation to one person.

Contributors

• James Prescott Joule · SCIENCE: Named source contributor; exact labor shares are not measured.

• Joule, On the mechanical equivalent of heat, Philosophical Transactions 140, 61–82 (1850), original paper copy

Provisional WRS assessment, edition 2026-10-16.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.

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