Mechanical equivalent of heat – who established the convertibility of heat and work? The statement that heat and mechanical energy are mutually convertible, supported by definitive experiments determining the mechanical equivalent of heat, was established by:

Introduction / Context:
Before the energy concept was unified, heat was treated as a separate “caloric.” James Prescott Joule’s experiments quantified the equivalence between mechanical work and heat, laying the groundwork for the First law of thermodynamics and modern energy conservation principles.

Given Data / Assumptions:

• Carefully measured mechanical work input to a system (e.g., stirring water).
• Observed temperature rise indicating heat generation.
• Isolation to minimize losses.

Concept / Approach:

Joule’s paddle-wheel experiments showed that a known amount of mechanical work produces a proportional temperature increase, establishing a constant mechanical equivalent of heat (often denoted J). This demonstrated that heat is a form of energy and is quantitatively convertible with mechanical work, a central tenet of the First law: ΔU = Q − W.

Step-by-Step Solution:

Verification / Alternative check:

Independent repetitions and alternate setups (electrical heating, compression heating) reproduce the equivalence, reinforcing Joule’s conclusion.

Why Other Options Are Wrong:

Boyle and Charles studied gas laws; Carnot analyzed ideal engine efficiency but did not establish numerical equivalence. “None of these” is incorrect.

Common Pitfalls:

Attributing the First law’s statement to Carnot; Carnot’s work concerns ideal cycle limits, not the equivalence constant.

Final Answer:

Joule