Design and Experimental Validification of Joule’s Experiment Using A Thermos Flask

Before 1840, heat was considered as a type of fluid. It was considered that heat was not a form of energy. In 1840, James Prescott Joule performed a series of experiment and concluded that heat is a form of energy and gave the relationship (W α Q) i.e., the ratio of work done to heat produced always remains constant, when mechanical work converted into heat and vice versa. The purpose of the study is to build a low-cost setup obtain the Joule’s constant using the thermos flask as a calorimeter. Different fluids like water, milk, etc is taken into the flask and work is done using blades driven by the electric motor. All the observations are recorded through the thermocouples fitted inside the thermos flask and we were able to obtain the joules constant also known as the mechanical equivalent of heat as 4.583 J/cal. The value obtained by Joule was 4.186J/cal. Thus, we were able to obtain the mechanical equivalent of heat with percent error of 9.5%