NEIEP Magnetism And Electromagnetism (355)

In an ideal transformer, power is conserved—there are no losses in the windings or core. That means the input power equals the output power: P_in = P_out. Since power is the product of voltage and current, this becomes Vp Ip = Vs Is. This direct equality captures the energy transfer happening inside an ideal transformer. The voltage ratio Vs/Vp = Ns/Np is another fundamental relation that describes how voltages relate to turns. From that and the power balance, you’d get the current ratio Is/Ip = Np/Ns, which shows currents are inversely related to the turns. The statement Vp/Ip = Vs/Is would imply equal input and output impedances, which isn’t generally true for different turns and loads. So the clean, universally valid way to state the power relationship is that input power equals output power.