Which device converts AC to DC?

• A. Rectifier
• B. Transformer
• C. Inductor
• D. Capacitor

Answer: (A)

Rectification is the process of turning alternating current into direct current, and a rectifier is the device designed to do that. It uses diodes, which conduct current in only one direction. When AC comes in, each half-cycle is allowed to pass in the same direction, producing pulsating DC. A single-diode setup gives half-wave rectification, while configurations with two or four diodes (a bridge) achieve full-wave rectification, using both halves of the waveform for a smoother output. After rectification, a filter capacitor is often added to smooth the pulsations and produce steadier DC, but the conversion from AC to DC happens in the rectifier. A transformer changes AC voltage but does not convert to DC, and inductors or capacitors alone do not convert AC to DC.