The Joule Machine was originally conceived as a measuring apparatus. James Joule built it in the 1840s for his famous measurement of the mechanical equivalent o

The Joule Machine was originally conceived as a measuring apparatus. James Joule built it in the 1840s for his famous measurement of the mechanical equivalent of heat: one Joule equals the amount of energy required to raise the temperature of 1 cubic centimeter of water by 1 degree Celsius. Although this confuses the definition of joule with calorie, Joule's experiment was brilliant and laid the groundwork for the laws of thermodynamics: https://en.wikipedia.org/wiki/Mechanical_equivalent_of_heat https://en.wikipedia.org/wiki/Mechanical_equivalent_of_heat A weight was suspended from a rope and allowed to fall. The falling weight was mechanically coupled to a paddle in a pool of water. As the weight fell slowly, it turned the paddle. Given that the mass of the weight and the water were known, the work performed by the falling weight and the heat absorbed by the water could be quantitated. Here's a kitchen test of the principle where a household blender is used to boil water: https://www.youtube.com/watch?v=GjcOobt9Ef8 https://www.youtube.com/watch?v=GjcOobt9Ef8 I suspect some heat transfer from the motor through the blades, but it's very surprising the water boils. He could have run a calculation, based on the power output of the blender, to see if the temperature increase was reasonable.