How does a transformer function in electrical systems?

A transformer operates by using electromagnetic induction to change the voltage of alternating current (AC) while maintaining the same frequency. When AC passes through a primary coil, it creates a magnetic field that induces a voltage in a secondary coil. Depending on the turns ratio between the primary and secondary coils, the transformer can either step up (increase) or step down (decrease) the voltage. This functionality is crucial in electrical systems for efficient power distribution, as it allows transmission of electricity over long distances at high voltages, which reduces energy losses.

The other options do not accurately describe the function of a transformer. For instance, converting direct current to alternating current refers to the process of inverter technology, not a transformer’s operation. Measuring electrical resistance involves instruments like ohmmeters, while storing electricity for future use typically involves batteries or capacitors, not transformers. Thus, the principal role of a transformer is specifically tied to adjusting AC voltage levels, making the given answer the correct one.