The spinning toilet brush–a classroom experiment on the mechanical equivalent of Joule’s heat

Abstract

Although Joule’s experiment on the mechanical equivalent of heat is well known and discussed in many introductory physics courses and textbooks, we are not aware of any version of this experiment that can be set up by lecturers or teachers using standard laboratory equipment. To fill this gap, we present a setup quite similar to Joule’s original experiment and show what kind of quantitative results can be obtained with it. It will be shown that temperature control is a major challenge, making Joule’s work even more impressive.