What device is used to convert alternating current (AC) to direct current (DC)?

A rectifier is the device specifically designed to convert alternating current (AC) into direct current (DC). This conversion is essential in many electrical applications, as different devices often require specific types of current for proper operation.

Rectifiers work by allowing only one half of the AC wave to pass through, effectively "clipping" the negative part of the waveform and producing a pulsating DC output. This process can be achieved using various configurations, such as half-wave or full-wave rectifiers, depending on the application and efficiency required.

Transformers, while crucial in altering the voltage levels of AC, do not convert AC to DC. They function solely by electromagnetic induction and do not change the nature of the current. Inductors are passive components that store energy in a magnetic field when electrical current passes through them but do not perform the AC to DC conversion. Transistors are semiconductor devices used to amplify or switch electronic signals but are not primarily used for the conversion between AC and DC. Thus, the rectifier stands out as the appropriate device for this specific conversion process.