Why Electricity is supplied in multiple of 11? Like 220V, 440V etc.

By chance, not everywhere has a multiple of 11.

Also, think about how you would change up or down the voltage? Why does this limit the numbers that the voltage can be?

Received in e-mail (please keep responses to this thread):

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Originally Posted by i_dinesh4u

Yes It is true that everywhere electricity is supplied in multiple of 11 but most of place it is limited to multiple of 11 specially in supply process? Please tell me why?

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"All European and most African and Asian countries use a supply that is within 10% of 230 V, whereas Japan, North America and some parts of South America use a supply between 100 and 127 V."

I see no indication of it always being a power of 11, as you seem to believe.

In the US, it has crept up to a multiple of 12, commonly 120, 240, 480. Many people still use the lower number. I am not sure how long ago it was lower.

I have asked to have this moved to electrical where you may get a better answer. I too suspect chance, just what some of George Westinghouse's early apparatus produced.

Note, glad somebody else posts emails to the board, complying with site policy.

Moved.

I also encourage you to think about the way that one would change up and down voltage, and why this might place a restriction on using multiples of a certain number within a country.

Post your thoughts and we can then give ours.

The ratio of voltages is equal to the ratio of the turns of the windings. Thus say a 24 volt control transformer will have 5 times as many primary as secondary windings. So you can do any ratio. It is common for lighting ballasts, a form of tranformer, to have leads for several voltages including 120, 208, 240, 277, and 480 inputs.

Power supply transformers may be a better example providing different taps to give different voltages to several circuits.