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    (Original post by Mehh)
    Vout = - n2dΦ/dt
    Iin n1 = Φ

    That all that is known for sure. The phase of Vin relative to Iin is dependant on the coil and the power supply. The phase of Vout relative to Iout is dependant on the secondary coil and the load(s). However for the most parts, I don't believe you need to know this for ALevel Physics. If you did need to know you would probabily know a wee bit about complex impediance [Z = V/I].
    so current and flux are in the same phase? And current and flux have a phase difference of pi/2 against voltage?

    As the formula for the magnetic field strength inside the solenoid (2 coils in the transformer are considered as 2 solenoids) B = µ.n.I
    And magnetic flux , Φ = NBA = µ.n.N.A.I
    So the flux should be in-phase with the current.
    Whereas, e.m.f, E = -dΦ/dt = -k.dI/dt (k>0)
    If I = Io.sin2πft -> dI/dt = Io.cos2πft = Io.sin(2πft + π/2)
    So it's obviously, the induced e.m.f is different π/2 relative to the current.
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