As we know from Deepak Mishra's article that a few to 100 Hz is enough for AC, Sir Nikola Tesla suggested that there are 60 minutes in 1 hour, 60 seconds in 1 minute, so there should be 60 cycles in 1 second. On the other hand Britishers thought that it would be nice to follow the cash system i.e. we have coins/notes for these amount :1, 2, 5, 10, 20, 50,100, etc. As 20 would be too low and 100 would be too high, so they selected 50 Hz.
NOTE. check Deepak Mishra article on why power frequency is limited to 50/60 Hz
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