ARRL Technician Practice Exam

What device is used to convert alternating current into varying direct current?

1. Capacitor

2. Rectifier

3. Transformer

4. Inductor

The correct answer is: Rectifier

The device used to convert alternating current (AC) into varying direct current (DC) is indeed a rectifier. Rectifiers work by allowing current to flow in only one direction, effectively "clipping" the negative half-cycles of the AC waveform. This process transforms the input AC signal into a pulsed DC signal, which can then be smoothed using filters (like capacitors) to produce a more consistent DC output. In practical applications, you often find rectifiers in power supply circuits where they are crucial for applications requiring a stable DC voltage derived from AC sources, such as in charging batteries or powering electronic devices that require a direct current. The other devices listed serve different functions within electrical circuits. A capacitor is used primarily for energy storage and filtering applications, a transformer is used to change the voltage levels of AC signals, and an inductor is typically involved in creating magnetic fields and filtering out frequency signals in AC circuits. Each of these has a unique purpose and does not inherently perform the function of converting AC to varying DC.