What does a transformer do with electrical power?

A transformer plays a crucial role in electrical power systems by transforming voltage levels while conserving the overall amount of electrical power. Its primary function is to either increase (step-up transformer) or decrease (step-down transformer) the voltage of alternating current (AC). This process allows electrical energy to be transmitted over long distances efficiently, as higher voltages reduce the current for a given power level, minimizing energy losses due to resistance in the wires.

The term "transform" is significant here, as it encompasses both the ability to increase and decrease voltage levels, depending on the design and purpose of the transformer. The power delivered remains approximately constant (considering minimal losses), meaning that if the voltage is increased, the current must decrease proportionally, and vice versa.

In the context of the other options, focusing solely on increasing or decreasing power without acknowledging the transformation of voltage levels is incomplete. Regulation is also a function that can be associated with transformers but is not their primary role, which is fundamentally about changing voltage levels rather than just stabilizing or controlling them. Thus, the most accurate representation of a transformer's function is its ability to transform voltage levels effectively and efficiently.