What are these power supply specifications?

The power supply of your computer lists these specifications on the label:

100-120V ~ / 4.0A
220-240V ~ / 2.0A

What does this information mean?

A) The power supply can support both 100-120V DC and 220-240V DC power sources.

B) The power supply can support both 100-120V AC and 220-240V AC power sources.

C) The power supply uses 4 amps of power when using a 220-240V AC power source.

D) The power supply uses 2 amps of power when using a 110-120V DC power source.

The answer: B) The power supply can support both 100-120V AC and 220-240V AC power sources.

Many computer power supplies are switched-mode power supplies that can support multiple voltage inputs. On these specifications, both 100 through 120 volt and 220 through 240 volt power sources are supported. Some power supplies can automatically switch between these input voltages and others have a physical switch on the outside of the power supply. You would normally switch the power input value based on your country’s power specifications.

The squiggly tilde (~) designates an alternating current (AC). If the specifications showed a solid line above a dashed line, it would be referencing direct current (DC).

The amperage used by the power supply will differ when using different voltages, so the input amperage is listed as different values at 100-120 volts versus 220-240 volts.

Want to know more? Watch “Computer Power Overview.”

Every computer system has a power supply, so the CompTIA A+ professional needs to have a solid understanding of personal computer power supply characteristics and types. In this video, you’ll learn about the basics of electricity (i.e., amp, volt, watt), the type of connectors you can expect to see on a power supply, and the industry standards that are used to perfectly match your motherboard with your power supply.