What happens to power in a step-up transformer?

In a step-up transformer, the primary function is to increase the voltage from the primary winding to the secondary winding while maintaining the power (the product of voltage and current). The principle behind this is based on the law of conservation of energy, which states that energy cannot be created or destroyed, only transformed.

When a transformer steps up the voltage, it does so by having more turns of wire in the secondary winding than in the primary winding. According to the transformer equation, the ratio of the voltages in the primary and secondary windings is directly proportional to the ratio of turns in each winding. As the voltage increases, the current on the secondary side must decrease to keep the power—the product of voltage and current—constant.

Thus, while the voltage increases in a step-up transformer, the power remains unchanged. This is crucial for efficient energy transmission across distances, as higher voltage can result in lower current, which helps reduce losses due to resistance in the wires.