What does a transformer do?

A transformer is a critical device in electrical systems that operates on the principle of electromagnetic induction. Its primary function is to change the voltage levels in an alternating current (AC) signal. By using two coils of wire, known as the primary and secondary windings, it can either step up (increase) or step down (decrease) voltage while maintaining the power level, minus any losses due to inefficiency.

This capability of a transformer to adjust voltage is vital for efficient power transmission over long distances, as higher voltages reduce losses associated with electrical resistance in wires. In addition to changing voltage, a transformer also affects current and impedance: when voltage is increased, current decreases, and vice versa, in accordance with the principle of power conservation.

Understanding these functions is crucial for electrical apprentices as they work with various electrical systems. The other choices describe different devices or functions not associated with transformers, underscoring the unique role transformers play in electrical engineering and power distribution.