True or False: In an ideal transformer, power is conserved (P = VI) so voltage changes on one side require proportional current changes on the other.

• A. True
• B. False
• C. Power does not depend on voltage or current.
• D. Cannot determine without load data.

Answer: (A)

In an ideal transformer, power in equals power out because there are no losses: P_in = V_in I_in = P_out = V_out I_out. The voltages on the two sides are tied to the turns ratio, V_out = V_in × (N_s/N_p). To keep the same power with that voltage relationship, the currents adjust inversely: I_out = I_in × (N_p/N_s). So if the voltage on one side changes, the current on the other side must change in the opposite way to keep the product VI the same. This is the essence of how an ideal transformer transfers power: the voltages and currents on the two sides move together to conserve power.