What is the difference between an alternator and a generator?

• A. They are both devices that produce electric power through mechanical input.
• B. An alternator generates DC power; a generator generates AC power.
• C. An alternator generates AC power while a generator can generate AC or DC power.
• D. An alternator is used only in automotive applications; a generator only in industrial settings.

Answer: (C)

The important idea is what kind of electrical output each device is designed to produce. An alternator is a specific type of generator whose output is alternating current. In many practical uses, that AC is then converted to DC or used as AC, depending on the system. A generator, in general, can be built to produce either AC or DC, with DC generators historically using a commutator to deliver direct current and AC generators using slip rings to provide alternating current.

This makes the correct choice the best because it states that the alternator inherently generates AC power, while a generator can generate either AC or DC power, depending on its construction. The other statements miss the key distinction: an alternator does not inherently produce DC (that requires rectification or a different design), and generators aren’t limited to one setting of applications—alternators are used in many places beyond automotive, and generators can be configured for DC as well as AC.