Final answer:
Alternators are rated in volt-amps, which is a measure of the apparent power. AC has the advantage over DC in voltage and current stepping up or down.
Step-by-step explanation:
The subject of this question is Physics as it relates to the concepts of alternators and alternating current.
Alternators are indeed rated in volt-amps, which is a measure of the apparent power produced by the generator. This apparent power represents the combination of both real power (measured in watts) and reactive power (measured in volt-amperes reactive or VAR).
Alternating current (AC) has the advantage over direct current (DC) that its voltage and current can easily be stepped up or down using transformers. Transformers use the principles of electromagnetic induction to increase or decrease the voltage levels of an AC signal while maintaining the same frequency.
Learn more about Alternators and Alternating Current