What device is responsible for increasing or decreasing the voltage of AC?

The device responsible for increasing or decreasing the voltage of alternating current (AC) is a transformer. Transformers operate on the principle of electromagnetic induction and are specifically designed to change voltage levels while maintaining the same power level, minus any losses. This transformation is achieved through the use of coils, or windings, where the ratio of turns between the primary coil (input) and the secondary coil (output) determines whether the voltage is increased (step-up transformer) or decreased (step-down transformer).

Transformers are critical components in power distribution systems, allowing electrical energy to be transmitted efficiently over long distances. By adjusting voltage levels, they minimize energy loss that occurs due to resistance in conductors. Other devices listed, such as rectifiers, converters, and regulators, serve different purposes. Rectifiers convert AC to direct current (DC), while converters can handle various types of voltage changes, but typically in the context of DC. Regulators maintain stable voltage output regardless of variations in input or load, ensuring that devices receive consistent power. However, none of these functions specifically pertain to the direct increase or decrease of AC voltage levels, which is the primary role of a transformer.