I'm required to test a harizontal axis turbine's performance and plot a RPM vs Power curve. The turbine is driving a small DC generator that produces 5V at the turbine's maximum RPM with no other load on the generator. I am planning on installing different sized resistors in parallel with the generator and then measuring the voltage out. This will effectively act as a load which will decrease the RPM, and in turn decrease the voltage produced by the generator, which can then give me a plot. My question is - what size resistors do I need? Through my study of wind/water turbines, I've calculated that the maximum power that this turbine can extract from it's environment is ~20W ideally. My attempt at answering my question was that I use P=V^2/R to rearrange for R=V^2/P=5^2/20=1.25Ω. So would I need resistors from 0Ω to 1.25Ω?