Physics for IGCSE & O level - Magnets And Currents (Section 5 - No. 16)

If the input voltage is 12 V and the output voltage is 24 V, what is the ratio of turns on the output coil to the turns on the input coil?

1:1

2:1

1:2

3:1

Since voltage is proportional to turns, a doubling of voltage implies a 2:1 turns ratio.