Why Does The Frequncy of USA & India is Diffrent ?

America is faster than India, Europe and many other countries. In USA politicians run for office. Our politicians stand for elections. Many similar small difference. So they need 60Hz.

now that everyone has made jokes (and some good ones too!) to answer your question it is mostly historical and it comes about because India used to be a British Colony and the UK used 50hz. as to which is more reasonable costwise depends on where you are and what frequency is used there. if you try to use a motor designed for 60 hz on a 50 hz system, you will get slower shaft speed and overheating. motors and transformers and solenoids and relays designed for 50 hz have more iron in them to compensate for the lower frequency. so from a manufacturing perspective these items are cheaper when designed for 60 hz because you save on iron, but the difference is not a lot. the bigger issue is that the US uses 120V per phase at a higher current whereas most of the rest of the world uses 240V at a lower current. this reduces the amount of copper required to carry the load (because wire size is driven by current, not voltage.), but the downside is that 240V is more likely to cause serious harm if a person is inadvertently shocked. 120V will hurt, but in many cases won't kill you. the 120V number was chosen by Westinghouse because during the fight for dominance between GE/Edison's DC system and Tesla/Westinghouse's AC system, Edison started a smear campaign about how dangerous AC electricity was so a voltage was chosen low enough that it was unlikely to kill anyone unless they were immersed in water or could not otherwise break the circuit. He'd hold public exhibitions and use AC to electrocute animals and even got the NY prison system to execute prisoners using an electric chair using AC to try to scare people into using his DC system, but AC won out.

For electronic devices (those without motors and such) the power supplies are usually able to deal with either one, often automatically, others need to have a switch thrown first, so all you have to do is plug in the appropriate line cord with the right plug ont he end and away you go. but for things with electric motors and such, it isn't so simple.