A.C for power transmission

[Jadaav]

Why is an alternating current used for long distance transmission of electrical power ?

What about direct current ?

 

[Emilyjoint]

It is because transformers can be used to transform AC voltage to high voltage to reduce power loss in connecting cables. High voltage means less current for the same power and therefore with highg voltage I^2r losses are reduced.
Transformers can then be used to step down the high voltage to safer values for domestic use.

 

[mathman]

http://en.wikipedia.org/wiki/Electric_power_transmission#High-voltage_direct_current

Above describes the use of direct current in long distance.