How to assemble a low voltage, variable speed electric motor in a school laboratory, and how to measure its efficiency?
For a high school physics project, I am doing an investigation on how does the density of the transmission fluid affect the efficiency of a fluid coupling. I am planning to use honey based transmission fluid with varying amounts of water to dilute it, and alter and manipulate its density. For the turbines (blades of the fluid coupling) I need to construct a low voltage electric motor with variable speeds using materials easily available in a school laboratory (though I can use some other source for my materials as well). I need to measure its efficiency. and by that I mean to actually compare the input and output energies (perhaps their voltages) using a low inertia dynamo as my output generator.