A transformer improves the overall efficiency of a distribution system by increasing usable power.

• A. True
• B. False
• C. Not enough data
• D. Only when stepping down voltage

Answer: (B)

Transformers change voltage and current to move power efficiently, but they do not create more energy. The power entering a transformer is roughly the power leaving it (minus small losses), so the device does not increase the total usable real power available to loads. The big gain comes from reducing current in the lines by stepping voltage up for transmission and down for local use; lower current lowers I^2R losses in conductors, which improves the overall efficiency of delivering the same amount of power. Because of that, saying a transformer increases usable power is misleading—the real power that can be delivered is determined by generation and losses, not by the transformer creating extra power. Stepping up or stepping down both contribute to efficiency, and transmission systems often rely on stepping up to reduce line losses.