CompTIA A+ Core 1 (220-1201) Practice Exam 2025 – Your All-in-One Guide to Exam Success!

Direct Current (DC) voltages used in computer systems are characterized by their stable and fixed values, which are essential for the proper functioning of hardware components such as the motherboard, processors, and peripherals. The commonly used DC voltages in computers are indeed 3.3 volts, 5 volts, and 12 volts. These voltage levels power critical elements of a computer, ensuring reliable operation.

Unlike alternating current (AC), which frequently changes its direction and amplitude, DC maintains a constant voltage level. This stability is crucial for electronic circuits that require a consistent power supply to operate without fluctuations that could potentially disrupt performance or damage components. Therefore, identifying the fixed nature of DC voltages, such as those mentioned, directly connects to how computers are designed to function with specific voltage requirements for different parts.

The other options describe AC voltages and variable power conditions, which are not applicable when discussing the DC power typically used in computers. AC is found in standard household electricity supplies, and variable voltages from transformers do not provide the steady supply required for internal computer components. High-frequency oscillating voltages pertain to radio frequency signals and alternating current applications rather than the stable DC voltages used in computing environments.