A.C. means alternating current, the current or voltage which alternates its direction and magnitude every time. Now a days 95% of the total energy is produced, transmitted and distributed in A.C. supply the reasons are the following.
1) More voltage can be generated than D.C. ( Up to 33,000 volts, when D.C. 650 volts only )
2) A.C. voltage can be decreased or increased with the help of static machine called the “Transformer”
3) A.C. transmission and distribution is more economical as line material (say copper) can be saved by transmitting power at higher voltage.
4) A.C. Motors for the same horse power as of D.C. motors are cheaper, lighter in weight, require lesser space and require lesser attention in operation and maintanence.
5) A.C.can be converted into D.C. easily. When and where required but d.c. can not be converted to A.C. so easily and it will not be economical.