As, the transformer works on the principle of mutual induction between two coils.So, according to Faraday's law,
induced emf=-number of turns in coil *[change in flux per unit time]
write above equation in formula form,
V= -N[ΔФ/Δt]
Now, write the above equation for both primary and secondary coils of transformer and equate them(as ΔФ/Δt remains same for both of them):
we get the relation:
V_{s} / V_{p}=N_{s} / N_{p}
s stands for secondary coil.
p stands for primary coil.
By putting the values:
V_{s}/25=60/20
V_{s}=75volts (output voltage).[tex] [/tex]
