In a transformer, what happens to current when voltage is increased?

• A. Current increases
• B. Current remains constant
• C. Current decreases
• D. Current fluctuates

Answer: (C)

In a transformer, the relationship between voltage and current is defined by the principle of conservation of energy and the turns ratio of the transformer. When the voltage on the secondary side of the transformer is increased, the current must decrease to maintain the same power level provided that the transformer is ideal and neglecting losses.

This relationship is governed by the formula: ( P = V \times I ), where ( P ) is power, ( V ) is voltage, and ( I ) is current. For an ideal transformer, the power on the primary side (input) must equal the power on the secondary side (output). Therefore, if the voltage increases on the secondary side, the current must decrease to keep the power consistent because ( P_{\text{primary}} = P_{\text{secondary}} ).

In practical terms, increasing the voltage leads the transformer to step down the current in order to keep the power level constant. Thus, the correct response reflects this fundamental principle of how transformers operate.