Starting from Faraday's Law (see Week 4 lecture notes), and assuming B(t) = Bp sin(\omega t), show that the magnitude of the EMF in the secondary coil Vsec is given by:
Vsec = N A Bp \omega ,
where A is the area of the primary coil, N is the number of secondary turns (20 here), Bp is the amplitude of magnetic field in the primary coil, and is the angular frequency of the field.