The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux φ linked with the primary coil is given by φ = φ0 + 4t, where φ is in Weber, t is the time in second and φo is constant, the output voltage across the secondary coil is
1
90 V
2
120 V
3
220 V
4
30 V