Why we Indians use only ac current?

Answer 1

Don't worry, anywhere in the world, house power is AC current. typically, the voltage ranges from 110V to 240V singlephased, and a frequency of 50 to 60Hz

The reason of AC (alternating current, swinging from a positive to a negative and back positive for 50 to 60 times per second) is that electricity has always been generated this way, it's easier to transform to lower or higher voltages, and is less dangerous than DC current.

generation: in generators, a rotary unit will generate current by moving a magnetic field over a conductor. This will generate electricity.
Transformation: a transformer can concert changing electromagnetic fields to another voltage-current with minimum losses.
transportation and safety: AC currents will cause vibrations in wires, but since 100 to 120 times per second, the voltage and current are zero, any electrical short or malfunctioning will stop for a short period of time.
DC will make your muscles cramp, eg. around an unprotected wire, and there is no way to let go. AC will shock you (100 times per second) but has a less 'sticky' effect.

Note a smaller amount of low frequency AC current will kill vs. AC. A study was done showing that 90mA of DC will cause "painful and severe shock, difficulty breathing, and loss of muscular control" by most male individuals. 60mA DC will do the same to most women. 23mA of 60Hz AC for men and 15mA of AC for women is roughly equivalent.