What is the voltage at its maximum value after a generator has completed a 90-degree turn?

The voltage at its maximum value after a generator has completed a 90-degree turn is indeed the positive peak. In an AC generator, the output voltage waveform is sinusoidal. At the beginning of the cycle (0 degrees), the voltage is at zero. As the rotor turns, the voltage rises from zero, reaches its maximum positive value at 90 degrees, and then continues to decrease toward zero and eventually becomes negative.

This process is based on the principles of electromagnetic induction, where the voltage induced in the generator is related to the angle of the rotor with respect to the magnetic field. At 90 degrees, the generator’s rotor is aligned in such a way that it creates the strongest magnetic field interaction, resulting in the maximum voltage output, or positive peak.

The other options are based on different points in the voltage cycle: zero at the starting point, negative peak occurs after 180 degrees, and average voltage represents a mean value over a complete cycle, which does not reflect the instantaneous maximum value. Therefore, the correct answer reflects the behavior of an AC generator at a specific point in its rotation.