What apparatus is used to change alternating current to direct current?

The apparatus that changes alternating current (AC) to direct current (DC) is known as a rectifier. This device functions by allowing the current to flow in only one direction, effectively converting the bidirectional flow of AC into a unidirectional flow of DC. Rectifiers often use diodes, which are semiconductor devices that permit current to pass in one direction while blocking it in the opposite direction.

This conversion is crucial in various applications, such as power supplies for electronic devices, where DC is required for operation. Rectifiers can be designed in different configurations, such as half-wave or full-wave, depending on the specific needs of the circuit.

While capacitors, regulators, and inverters all play important roles in electrical circuits, they do not serve the function of converting AC to DC. Capacitors are typically used for filtering and smoothing voltage levels, regulators stabilize output voltage, and inverters perform the opposite function by converting DC back to AC. Therefore, the rectifier is the correct choice for the task of changing alternating current to direct current.