Which device is used to convert AC into DC?

The device that is used to convert alternating current (AC) into direct current (DC) is indeed a diode. A diode is a semiconductor device that allows current to flow in one direction only. When AC voltage is applied to a diode, it conducts during the positive half-cycle of the AC wave while blocking the negative half-cycle. This process is known as rectification.

In a typical rectifier circuit, multiple diodes can be arranged in various configurations (such as a bridge rectifier) to efficiently convert the entire AC waveform into a pulsating DC output. Although additional components, like capacitors, are often used to smooth the output and create a more constant DC level, it is the diode that fundamentally enables the conversion from AC to DC by controlling the direction of the current flow.

Transistors, capacitors, and inductors serve different functions in electronic circuits; transistors are mainly used for amplification and switching, capacitors are energy storage components that can smooth out voltage fluctuations, and inductors store energy in a magnetic field when current flows through them. Thus, these devices do not perform the specific function of converting AC to DC as effectively as diodes do.