A transformer has primary voltage of 240v and a secondary voltage of 48v what is the turns ratio of this transformer?

The turns ratio of a transformer is directly proportional to the voltage.

To find the number of turns in the secondary, first calculate the voltage ratio.

24V/115V is a 1:0.2087, if we use this ratio to calculate the turns we get.

345 x 0.2087 = 72 turns.

Another idea to apply (which says the same thing) is that the ratio of the voltages will equal the turns ratio. Here's how that looks:

Voltageprimary / Voltagesecondary = Turnsprimary / Turnssecondary

or just

Vp / Vs = Tp / Ts

Plugging in the numbers will give us

115 volts / 24 volts = 345 turns / Ts , and 115/24 = 345/Ts , and 115 x Ts = 24 x 345 , and Ts = (24 x 345) / 115 , and Ts = 8780 / 115 = 72 turns.