Question

question: the voltage supplied by a/an ____ generator periodically changes from positive to negative.

Explanation:

In physics (a subfield of Natural Science), an alternating - current (AC) generator produces a voltage that periodically reverses its polarity, meaning it changes from positive to negative. Direct - current (DC) generators produce a voltage that has a constant polarity (or changes in a non - periodic, one - way - like manner for some types of DC generation, but not the periodic positive - to - negative change). So the generator in question is an AC (alternating - current) generator.

Answer:

alternating - current (or AC)