What is the purpose of a transformer in an electrical system?

A transformer is a crucial device in electrical systems primarily designed to modify voltage levels in alternating current (AC) circuits. Its foundational purpose is to increase or decrease the voltage according to the needs of the electrical system. When the electrical energy travels through the primary coil, it generates a magnetic field that induces a current in the secondary coil, either elevating or lowering the voltage depending on the coil ratio.

For example, in power distribution systems, transformers are used to step up voltage for long-distance transmission, which helps reduce energy loss due to resistance in the wires. Conversely, they are also employed to step down voltage levels for safe use in residential or commercial applications. This versatility in managing voltage is critical for efficient energy distribution and utilization.

The other options touch on different aspects of electrical safety and functionality but do not capture the primary function of a transformer. Grounding circuits helps prevent electrical shock hazards, interrupting excessive current refers to devices such as circuit breakers, and facilitating safe discharge of current relates more to grounding or surge protection devices rather than the voltage transformation process performed by a transformer. Thus, the central and defining function of this device is indeed to manage voltage levels within an AC electrical system.