Direct current (DC) is an electrical current that flows consistently in one direction.
The current that flows in a flashlight or another appliance running on batteries is a direct current
Alternating Current [AC]:
An alternating current can be defined as a current that changes its magnitude and polarity at regular intervals of time.
It can also be defined as an electrical current that repeatedly changes or reverses its direction opposite to that of a direct current or DC which always flows in a single direction as shown below.
Advantages of alternating current (AC) over direct current (DC):
AC is easy and cheaper to generate than DC.
AC can be transferred to long distances as compared to DC. Long-range transmission results in relatively low energy losses resulting from resistance.
Power loss in AC is less as compared to DC during transmission.
AC can be easily converted into DC with the help of rectifiers.
AC can be relatively easily and economically stepped up or down with a transformer to suit the application. DC cannot be wired through a transformer.
Because it can be stepped up (and down), AC can be increased to high voltage levels for transmission over large distances, then stepped down to safer levels for consumer use.
High voltages can be generated in AC. This is more difficult with DC
