Ham Radio General Class Practice Test

Which of the following types of capacitors are often used in power supply circuits to filter the rectified AC?

1. Disc ceramic

2. Vacuum variable

3. Mica

4. Electrolytic

The correct answer is: Electrolytic

Electrolytic capacitors are commonly used in power supply circuits for filtering rectified AC because they have a relatively high capacitance value compared to other types of capacitors. This high capacitance allows them to store a significant amount of electrical energy, which is essential in smoothing out the fluctuations in voltage after the AC has been rectified. In a power supply, after the AC voltage is converted to DC through rectification, there are still ripples in the output voltage. An electrolytic capacitor effectively reduces these ripples by charging and discharging, thus providing a more stable DC voltage. Their design enables them to handle the necessary voltage and capacitance values for these applications, which is critical for effective filtering. Other types of capacitors, such as disc ceramic, vacuum variable, and mica, generally have lower capacitance values or are used in other applications, such as high-frequency circuits or tuning circuits, making them less suitable for the specific task of filtering in power supply scenarios.