In an ideal transformer, which statement is true about power on primary and secondary?

In an ideal transformer, which statement is true about power on primary and secondary?

• A. P_primary equals P_secondary
• B. P_primary greater than P_secondary
• C. P_primary less than P_secondary
• D. P_primary equals V_primary / V_secondary

Answer: (A)

Power conservation is what an ideal transformer relies on. In an ideal transformer there are no losses, so the power that flows into the primary must equal the power that flows out of the secondary. Since power is P = V × I, the input power is Vp × Ip and the output power is Vs × Is. The turns ratio gives Vs/Vp = Ns/Np and Is/Ip = Ns/Np (inverse), which leads to Vs × Is = Vp × Ip. Therefore, P_primary equals P_secondary. So, this means the primary and secondary powers are the same in the ideal case. The other statements would either mix up the relationships of voltage and current or treat power as something determined only by voltages, which isn’t correct for power transfer in a transformer. Real transformers have small losses, so P_primary is slightly greater than P_secondary, but the ideal model is exact in stating equality.

Power conservation is what an ideal transformer relies on. In an ideal transformer there are no losses, so the power that flows into the primary must equal the power that flows out of the secondary. Since power is P = V × I, the input power is Vp × Ip and the output power is Vs × Is. The turns ratio gives Vs/Vp = Ns/Np and Is/Ip = Ns/Np (inverse), which leads to Vs × Is = Vp × Ip. Therefore, P_primary equals P_secondary.

So, this means the primary and secondary powers are the same in the ideal case. The other statements would either mix up the relationships of voltage and current or treat power as something determined only by voltages, which isn’t correct for power transfer in a transformer. Real transformers have small losses, so P_primary is slightly greater than P_secondary, but the ideal model is exact in stating equality.