what is the main difference between DC n AC current???

AC is the short form for Alternating Current. The current that changes its polarity with time is called an alternating current. The current in your home’s main line is an alternating current.

DC is the short form for Direct Current. The current that stays constant with time is called direct current. Current from a battery is direct current.

Some differences:

1. AC can be transported over long distance at high voltage and low current so as minimizing the ohmic loss in heat while the same is not efficient for DC.
2. AC can be used as carrier waves for signal transmission purposes without the need of oscillators. While DC can’t be used for such purpose.
3. AC needs rectification before use in any electronic appliance while DC can be directly used with electronic components without the need of rectification.