Hi, am new member of this site. i have some querries...can u pls clear that...
In INDIA we use 220V,50 Hz supply... In other countries we have 110V,60hz supply... can u say me the reason for that... or correct my answer if am wrong...
P=VI ---- (1) energy can neither be created nor be destroyed,so Power value cannot be increased or decreased... so V and I goes indirectly proportional... When voltage increases,Current decreases and vice versa... But V=I/R ----(2) R=PL/A ---- (3) in India we use high volt,low current as bcos,the length of transmission can be increased at the same time size of the conductor is decreased,resulting in low cost.but only thing is resistance is decreased,so that it may cause danger to humanbeing.But in other country,they respect human life,thus resistance is increased...
but my question is...according to equation 2,when current is decreased voltage is increased...then how resistance is increased...if not in what concept they say resistance is decreased in equation (2)...pls do explain me guys and lass...

You are making it more complex than is necessary, and it has nothing to do with differences in respect for human life.

The only reason why voltages are different in different parts of the world is mainly an accident of timing with regards to electric lighting.

When Nikola Tesla worked with George Westinghouse to develop and install the first AC power system in Niagara Falls New York, he chose a voltage that he felt could be used with the existing DC power systems already installed by Edison's General Electric Co. Edison's new electric lights worked on 110VDC, so Tesla made his system 110VAC. Everything in the US developed from that. He (later) picked 60Hz because he was thinking of a clock and dividing it into equal segments to make calculations easier, so since there were already 60 seconds in a minute and 60 minutes in an hour, he made it 60 cycles in a second.

In Europe, specifically Germany, Werner von Siemens had invented the first electric dynamo (contrary to the belief that Edison had done so). Siemens' dynamo was for use in running the first electric powered cable cars, so he picked 220VDC because he could use smaller motors at the higher voltage. Lighting systems were then developed to take advantage of Siemens' dynamo, so they were 220VDC as well, and when AC power distribution began to spread across Europe, 220VAC became the norm. The 50Hz came from the fact that 50 cps = 20ms per cycle, a nice neat "metric" sounding number that can be easily divisible.

Once any individual country paid to electrify themselves, they had to buy their equipment from a neighbor who was already making it. So when Canada was developing their grid, they followed US norms so that Westinghouse's or Edison's (once he succumbed to AC) equipment would work.. The same was true for Mexico. European countries (and their colonies such as India was at the time), tended to favor whatever Europe was using.