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ASVAB · Components and Devices

What is the difference between AC (alternating current) and DC (direct current)?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

DC flows in one direction only; AC periodically reverses direction — in the US, household AC reverses direction 120 times per second (60 Hz)

  1. A AC is used only in batteries; DC is used in power lines
  2. B AC is stronger than DC
  3. C DC flows in one direction only; AC periodically reverses direction — in the US, household AC reverses direction 120 times per second (60 Hz)
  4. D They are the same except for voltage level

Why this is the answer

DC (Direct Current): Electrons flow in one consistent direction — positive terminal to negative terminal (conventional current). Source: batteries, solar cells, fuel cells. Used in: all electronics, electric vehicles, USB devices. AC (Alternating Current): Direction of electron flow reverses periodically. US standard: 60 Hz (60 cycles per second = 120 direction reversals/second); European standard: 50 Hz. Used in: power grid transmission (more efficient for long-distance), motors, household appliances.

Conversion: DC → AC: Inverter; AC → DC: Rectifier (diodes). The power adapter for your laptop converts AC wall power to DC for the device.

Source: ASVAB EI, AC vs DC

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About this topic: Components and Devices

Components and devices questions cover what resistors, capacitors, inductors, diodes, transistors, transformers, fuses and switches do, and their schematic symbols. Recognising a symbol and naming its job is most of the section. This is one of 19 Electronics Information questions on components and devices, each with a full explanation on a single study page.

New to this exam? Our ASVAB exam guide explains the format, scoring, and how to prepare.

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