The ratio of turns in primary to that in secondary for a transformer is 5 : 1 and power delivered by it is 500 W. What is the current in primary coil if a current of 12.5 A is flowing in the secondary coil?

The transformer in question is ideal and hence it has no power losses. This gives usPin =Pout ⇒V1I1=V2I2 … (i)  Given that Pout =500W and I2 = 12.5 A.But, Pout = V2I2⇒V2=P2I2=50012.5=40VAlso, given N1N2=51 (Turns ratio) For an ideal transformer, N1N2=V1V2⇒V1V2=51V140=51 ∵V2=40V⇒V1=200VForm (i), we have⇒V1I1=V2I2⇒I1=V2I2V1=40(12.5)200=2.5A