0.36 ohms.
1. R=(V^2)/P, where R represents the resistance of the unloading resistor (in ohms), V represents the rated voltage of the generator (in volts), and P represents the power generation The rated power of the machine (in watts).
2. The rated voltage of the 400-watt wind turbine is 12 volts. According to the above formula, the estimated value of the unloading resistance can be obtained: R=(12^2)/400=0.36 ohm.