Which device is used to convert AC to DC?

The device used to convert alternating current (AC) to direct current (DC) is a rectifier. A rectifier functions by allowing current to flow in only one direction, effectively transforming the bidirectional flow of AC into a unidirectional flow of DC. This process usually involves the use of diodes, which are components that permit current to flow only in one direction.

Rectifiers can be found in various forms, including half-wave and full-wave configurations, each providing different efficiencies for converting AC power to DC. This conversion is critical in many applications, such as power supplies for electronic devices, where stable DC voltage is required.

Transformers, while they can modify AC voltage levels, do not convert AC to DC. Inverters, on the other hand, do the opposite of what a rectifier does by converting DC back to AC. Capacitors are used for filtering and energy storage but do not perform a conversion between AC and DC currents. Therefore, the rectifier is specifically designed for this conversion process, making it the correct choice in the context of your question.