Which component rectifies the AC output of a power transformer to direct current?

The component that rectifies the AC output of a power transformer to direct current is the power diode. Diodes allow current to flow in one direction while blocking it in the opposite direction, which is the fundamental operation required for rectification. When the alternating current (AC) output from the transformer passes through the power diode, it effectively converts the AC signal, with its positive and negative cycles, into a unidirectional current flow, thus producing direct current (DC). This operation is crucial in power supplies, where a stable DC output is required for various electrical devices and applications.

The other components listed serve different functions in electrical circuits. Capacitors are primarily used for filtering and energy storage, smoothing out the ripples in the DC output after rectification. Inductors are used to store energy in a magnetic field and can filter or regulate current but do not perform rectification. Voltage multipliers are circuits that increase the voltage level of AC or pulsed DC but do not inherently rectify the current. These distinctions illustrate why the power diode is the correct choice for the function of converting AC to DC.