What does a transformer do?

A transformer primarily functions to increase or decrease voltage levels in alternating current (AC) systems. It operates based on the principle of electromagnetic induction, utilizing coils of wire wound around a magnetic core to transfer electrical energy between two circuits through the change in magnetic fields.

When the primary coil receives an AC voltage, it creates a magnetic field that induces a voltage in the secondary coil. The voltage transformation ratio is determined by the number of loops in the primary coil versus the secondary coil. For instance, if the secondary coil has more turns than the primary, the transformer will step up the voltage; conversely, if it has fewer turns, it steps down the voltage.

This capability is essential in power distribution systems, where it allows for efficient transmission of electrical energy over long distances by utilizing high voltage to reduce current and thereby minimize energy loss due to heat.

The other options refer to functions that are not characteristic of a transformer. For example, transformers do not convert AC to DC; they don't act as safety devices like circuit breakers but rather facilitate voltage adjustment; and they do not regulate the flow of electricity, which is typically the role of devices like resistors and controllers.