James Prescott Joule e o equivalente mecânico do calor: Reproduzindo as dificuldades do laboratório

Abstract

Despite many controversies, Joule's paddle-wheel experiment is considered crucial to demonstrate the conservation of energy in the classroom. However, the complexity of the experiment in its epoch is neglected and only the final result is presented, wasting an excellent moment to discuss with students all the hypotheses and subtleties involved in it. In this work we present the process of replication of Joule's 1850 experiment on the mechanical equivalent of heat. We used present-day devices. The hypotheses elaborated during the experiment as well as the data analysis demonstrate the complexity of science and the role of the experiment to validate theories. Also, this replication explores the difficulties in reaching an exact value for the mechanical equivalent of heat. Our intention is to show how historical experiments can collaborate to transform the experimental activity in the classroom into a rich environment to argumentation and inquiry-based teaching. © Sociedade Brasileira de Física.