A hair drier uses 9 A at 120 V. It is used
with a transformer in England, where the line
voltage is 237 V.
What should be the ratio of the turns of the
transformer (primary to secondary)?

Question

A hair drier uses 9 A at 120 V. It is used
with a transformer in England, where the line
voltage is 237 V.
What should be the ratio of the turns of the
transformer (primary to secondary)?

radar · Answer

You require a step-down with a ratio of 237:120  or about 2 to 1  (1.975 to 1)

anonymous · Answer

Thank you! @radar how would I determine the current it draws from the 237 V line?

radar · Answer

I will never feel the 237 volts, as the transformer will present 120 volts to it.  Oh I see what you mean, the current drawn on the 237 volt mains will be (120/237) (9) or approximately 4.5 A