What component changes 120 V AC power to a lower AC voltage for other uses?

A transformer is an electrical component consisting of two or more coils of wire wrapped around a common magnetic core. It works through electromagnetic induction to change (step up or step down) AC voltage levels. To convert 120 V AC from a standard wall outlet to a lower AC voltage for electronics, a 'step-down' transformer is used. The other components do not change AC voltage levels. A variable capacitor stores energy and tunes circuits, a transistor amplifies or switches current, and a diode allows current to flow in only one direction. While a diode is used after the transformer in a power supply to convert AC to DC, it is the transformer that lowers the AC voltage first.