Updated Almost the whole of the world uses a frequency of 50Hz and a voltage of 220-240(higher voltages for better efficiency in transmission). The exception, where 60Hz is used (with a voltage of 110-120), is the Americas (North and South) and the Caribbean (and parts of Japan and Korea).The reasons for India's A.C (ALTERNATING CURRENT) frequency is maintained at 50Hz are-IT STARTS FROM THE BEGINNING OF ELECTRICITY-Early in the history or electricity, Thomas Edison's General Electric company was distributing DC electricity at 110 volts in the United States. Then Nikola Tesla devised a system of three-phase AC electricity at  240 volts. Three-phase meant that three alternating currents slightly out of phase were combined in order to even out the great variations in voltage occurring in AC electricity. He had calculated that 60 cycles per second or 60Hz was the most effective frequency. Tesla later compromised to reduce the voltage to 120 volts for safety reasons.With the backing of the Westinghouse Company, Tesla's AC system became the standard in the United States.

Westinghouse chose 60 Hz because the arc light carbons(arc lamp) that were popular at that time worked better at 60 Hz than at 50 Hz.Europe goes to 50Hz and 230VMeanwhile, the German company AEG started generating electricity and became a virtual monopoly in Europe. how much do carrier ac units costThey decided to use 50Hz instead of 60Hz to better fit their metric standards, but they stayed with 120V.ac window unit installation nycEurope stayed at 120V AC until the 1950s, just after World War II. air conditioning unit replacementThey then switched over to 220V for better efficiency in electrical transmission. Great Britain not only switched to 220V, but they also changed from 60Hz to 50Hz to follow the European lead. Since many people did not yet have electrical appliances in Europe after the war, the change-over was not that expensive for them.

U.S. stays at 120V, 60HzThe United States also considered converting to 220V for home use but felt it would be too costly, due to all the 120V electrical appliances people had. A compromise was made in the U.S. in that 240V would come into the house where it would be split to 120V to power most appliances. Certain household appliances such as the electric stove and electric clothes dryer would be powered at 240V.India got 50Hz, because it was colonized by England, which when they developed their electrical systems, choose 50 Hz.From technical point of view operating 50 Hz versus 60 Hz would not make much difference but, to achieve it, either the prime movers - for example steam turbines, gas turbines and diesel engines  would need to be able to tolerate a 20% increase in speed or the alternators they drive - which produce the electricity  would need to be completely rebuilt with extra poles and windings so that they could continue to run at the same rotational speed. The costs of doing such re-engineering would be enormous and could not be justified as "economically worthwhile" from the point of view of actual necessity.

We  could have chosen any other frequency other than 50/60 hz but50/60 HZ is an optimum frequency which keeps the transmission losses to tolerable limits. The higher will be the frequency, the more will be the losses.and lower frequencies would causes the size, weight & hence the cost to increase. Also, more flickers are noticed in lesser frequencies than higher frequencies.The voltage and frequency of AC electricity varies from country to country throughout the world. Most use 220V and 50Hz. About 20% of the countries use 110V and/or 60Hz to power their homes.220V and 60Hz are the most efficient values, but only a few countries use that combination. EDIT-There is not any big scientific or electrical reason  as to why in US and some other parts of the World use 60Hz and in India and certain other parts of the World use 50 Hz.It is just the way it has been started and it continues so.Changing this system would cost a lot.                  Written It may be one of the following reasons: It may In US, the frequency is 60Hz and 110V supply, but in India is about 240V, 50Hz supply.

For a particular load say 100kW the current will be 0.416A. But in US the same load will consume about 0.9A. Here the thing is the heat produced in the cable because of the flow of current will be large in US compare to India. Since US is a cold country they can use this level but not in India.Moreover, once standardisation is fixed for Indian (50Hz) by British, so its continuing and in America its 60 Hz according to their standardisation.Its only because, too low value will create fluctuation in apparatus like Bulb starts blinking(persistence of eye is 15 Hz) and too high value will lead more hysteresis and eddy current losses in many machines.Written I am not a subject matter expert on this .But I found these links helpfulWhy the suply frequency in INDIA is 50HZWhy only 50 hz frequency is used in india? - Yahoo Answersor the similar Quora question.Why is supply frequency 50 Hz in India not 60 Hz?Written Probably its because they bought their original generating plants from Europe, most probably a UK firm.

They quoted what they were most familiar with building and it was 50 Hz power generators.Written Image courtesy: Graphs, InfographicsThe tussle between Nikola Tesla and Thomas Edison is heard by most of us. It is believed that Edison’s early experiments with the Direct Current (DC) power somewhere in late 1800s showed first mainstream application for electricity, however it suffered from a tendency to lose voltage over long distances. On the other hand Nikola Tesla invented something called Alternating Current (AC) power which can be easily transmitted over long-distance, this was a direct competition to Edison’s Technology and it happened to be 110V. It is also believed that 110V is more economic and during the earlier times electricity was delivered to homes and businesses for the sole purpose of lighting. The other electrical equipment came much later. At that time effective form of a light bulb was a carbon filament bulb that operated best at 100-110V. There was a lot of tussle between Edison and Tesla, words were exchanged, Elephants were electrocuted, and eventually it was settled that AC power was the only option.

The first company to buy Tesla’s patents for power transmission, Westinghouse Electric (founded by George Westinghouse) settled on an easy standard: 60Hz – 110V. Now the frequency of the AC supply depends upon the design and the rotatory speed of the generator. Generators operated by slow speed engines will produce lower frequencies, for a given number of poles, than those operated by for example a high speed steam turbine, these factors plays an important role to decide the operating frequency.However in Europe, specifically in Germany, BEW exercised their monopoly to push things a little further and they arbitrarily set 50Hz as frequency and increased the voltage up to 240V to improve distribution efficiency. This slowly spread to entire Europe. This standard was adopted by India as well. This however led to the world being divided into two frequency standard. Most 60Hz systems are nominally 120V and most 50Hz systems are nominally 230V.Courtesy: Complete list: Plug, socket & voltage by country - World Standards Giz Explains: Why Every Country Has a Different F#$%ing PlugUpdated Almost the whole of the world uses a frequency of 50Hz and a voltage of 220-240(higher voltages for better efficiency in transmission).

The exception, where 60Hz is used (with a voltage of 110-120), is the Americas (North and South) and the Caribbean (and parts of Japan and Korea).IT STARTS FROM THE BEGINNING OF ELECTRICITY-Early in the history or electricity, Thomas Edison's General Electric company was distributing DC electricity at 110 volts in the United States. India got 50Hz, because it was colonized by England, which when they developed their electrical systems, choose 50 Hz.From technical point of view operating 50 Hz versus 60 Hz would not make much difference but, to achieve it, either the prime movers - for example steam turbines, gas turbines and diesel engines  would need to be able to tolerate a 20% increase in speed or the alternators they drive  which produce the electricity  would need to be completely rebuilt with extra There is not any big scientific or electrical reason  as to why in US and some other parts of the World use 60Hz and in India and certain other parts of the World use 50 Hz.It is just the way it has been started and it continues so.

Updated When DC was used in USA, Edison used three wires of +110V, 0V and -110V.  There was a campaign by  Edison to portray AC as dangerous to human beings. 120V (110V) became the standard for AC  distribution in USA presumably because it used the "safer" Voltage level of the  DC system. 230V has lower distribution costs and thus was popularly taken up by Europe. India followed UK and thus India also use 240V (230V).Answered previously here:Arunava Chatterjee's answer to Why is electricity in the USA 110v when the rest of world uses 230v?[22] in 1898 and Kolar Gold Fields in 1902. You can read more about history of electricity in India from Reliance Power page History and evolution :: From these, we can Clearly say that India were following British standard of electricity (230 V 50Hz).But Why USA uses 120v 60Hz??[Source:  Could anybody tell me why the domestic supply is chosen usually as...]Early in the history or electricity, Thomas Edison's General Electric Company was distributing DC electricity at 110 volts in the United States.

Then Nikola Tesla devised a system of three-phase AC electricity at 240 volts. He had calculated that 60Hz was the most effective frequency. Tesla's AC system became the standard in the United States. why USA still uses old standards?because, it is very difficult and very costly to migrate to new standard.As compared India, USA  uses thick wire (For transferring same power, USA needs low resistance wire (means Thicker wire) compared to 230V system), on the other hand 110v is less harmful than 230v.More Readings Worldwide AC Voltages and Frequencies by Ron KurtusWritten if we use 230v,50hz for a load say 100kw. the current for this supply will be small when compared with 110v, 60hz.But the cable size for 110v,60hz is large due to insulation size.An  interesting thing is, only the cold countries will use 110v,60hz supply because the heat dissipated due to large current will acceptable to their climatical condition but not for india.. so the supply is depended upon the country, climatical condition and about adv & disadv........