Physics for IGCSE & O level - Magnets And Currents (Section 6 - No. 21)
In a transformer, the ratio of the input voltage to the output voltage is equal to the ratio of:
turns on output coil to turns on input coil
input current to output current
output current to input current
turns on input coil to turns on output coil
Selitys
The ratio of voltages is directly proportional to the ratio of the number of turns in the coils.