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5.66: Direct and Alternating Current

Difficulty Level: At Grade Created by: CK-12
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To use an electric appliance, you have to plug it into an outlet unless it has batteries. This may be all you need to know in order to use electric current. But did you ever wonder what electric current is or how it flows through wires inside the walls of your home? Electric current is a continuous flow of electric charges. The charges may flow in just one direction, or they may keep reversing direction. You can watch an animation of both types of current at this URL: http://www.youtube.com/watch?v=JZjMuIHoBeg

Direct Current

When current flows in just one direction, it is called direct current (DC). The diagram below shows how direct current flows through a simple circuit. An example of direct current is the current that flows through a battery-powered flashlight. In addition to batteries, solar cells and fuel cells can also provide direct current.

Alternating Current

When current keeps reversing direction, it is called alternating current (AC). You can see how it works in the two diagrams below. The current that comes from a power plant and supplies electricity to homes and businesses is alternating current. The current changes direction 60 times per second. It happens so quickly that the light bulb doesn’t have a chance to stop glowing when the reversals occur.

Q: Which type of current flows through the wires in your home?

A: Alternating current from a power plant flows through the wires in a home.


  • Direct current (DC) keeps flowing in just one direction. Batteries provide direct current.
  • Alternating current (AC) keeps reversing direction. Power plants provide alternating current.


  • alternating current (AC): Electric current that keeps reversing the direction in which the current flows.
  • direct current (DC): Electric current that flows only in one direction.


At the following URL, watch the video comparing direct and alternating current. Then answer the questions below. http://www.diffen.com/difference/Alternating_Current_vs_Direct_Current

  1. Current from a battery is __________ current.
  2. Current from a power plant is __________ current.
  3. In the U.S., alternating current reverses direction at a rate of __________ hertz.
  4. What is the advantage of producing and using alternating current?
  5. How can a device, such as a computer, that needs direct current use alternating current from a wall outlet?


  1. Compare and contrast direct and alternating current.

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alternating current (Abbreviation: AC) Electric current that keeps reversing the direction in which the current flows.
direct current (Abbreviation: DC) Electric current that flows only in one direction.

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Difficulty Level:
At Grade
7 , 8
Date Created:
Nov 01, 2012
Last Modified:
Sep 13, 2016

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