If a transformer is to be used to step up voltage from 120 volts to 240 volts, what must the turns ratio be?

Question

if a transformer is to be used to step up voltage from 120 volts to 240 volts, what must the turns ratio be?

please supply formula

Answer 1

i bought two numark ttx usb turntables of ebay with no warranty, they were from the usa. one of the turntables works fine the other did not even turn on at all. i thought it must be that i did't flivk the switch underneath from 110 to 230 volts. i took it in to my local numark dealer for repair and they said i neaded a new transformer. they didnt call me for a month so i went back to them and they said that i need something that comes before the transformer and you cant buy this part because the machines built totally different if there for 230 volts