how exactly does ac generator used? do we have D.C generator ?

Question

how exactly does ac generator used? do we have D.C  generator ?

anonymous · Answer

A.C generators are the most common method of producing electric power . A.C  can be used to transmit power over a very large distance without much lose. 
D.C generators are also available and structurally commutator is the only difference between A.C and D.C generators

anonymous · Answer

Above is correct but just to mention, there is a way to produce dc without a commutator: just rotate a disk in a magnetic field: http://en.wikipedia.org/wiki/Homopolar_generator DC too can be used to transfer power, and actually for very long distances, it is much more better technology than AC power transfer: http://en.wikipedia.org/wiki/High-voltage_direct_current