How is DC generated differently than AC?

Answer 1

DC is either generated as an AC voltage, such as your car's alternator and then rectified, or DC is generated by the use of a commutator that basically keeps only one set of coils connected to the load at any given point of time. This allows the load to only see one coil at a time, and only one current path at any given time. Rectification of an AC voltage is just the easier way to do it.

Answer 2

For commercial power generation, the generators "look" basically the same on the outside. It's how they are wired inside, the way the magnetic poles are used, and how many poles are inside, that creates either DC or AC. (Sometimes DC generators use commutators -- but that's on the 'inside' too).

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