Which conversion is NOT performed by a rectifier?

A rectifier is an electronic device that primarily serves the function of converting alternating current (AC) into direct current (DC). This process is essential in various applications where a stable DC supply is required, such as in power supplies for electronic devices. Therefore, the primary role of a rectifier is to facilitate this conversion from AC to DC.

Among the provided options, the conversion from DC to AC is not a function performed by a rectifier. Instead, such a conversion requires an inverter, which is designed specifically for that purpose. This distinction highlights the specialized role of rectifiers in electrical circuits.

The other provided options relate to functions typically associated with rectification, such as changing voltage levels and modifying currents, often in the context of how the rectified output is handled in circuits. However, the definitive role of a rectifier revolves around converting AC to DC.