The Basic Facts About Direct (DC) and Alternating (AC) Current

What is Direct Current (DC)?

Direct Current (DC) flows in the same direction all the time through an electric circuit. Electrons flow continuously through the circuit from the negative terminal of the battery to the positive terminal. Even when no current is flowing through the wire, the electrons in the wire are moving at speeds up to 600 miles (1000 kilometers) per second but in random directions because the wire has a finite temperature. Since one electron is moving back along the wire at the same time another is moving forward, no net charge is transported along the wire. If a battery is hooked to the ends of the wire, the electrons get pushed all in the same direction along the wire. The speed of the electrons along the wire is less than an inch (few millimeters) per second. So it takes any single electrons a long time to get all the way around the circuit. But there are so many electrons that they bump into one another, like dominoes, and there is a net shift of electric charges around the circuit that can happen at speeds up to the speed of light.

What is Alternating Current (AC)?

The outlets in our homes provide alternating current (AC). 60 times every second the electrons in the wire change direction. The electrical devices we use don't care which direction the electrons are moving, the same amount of current flows through a circuit regardless of the direction of the current.

Space Weather Effects?

Electric power distribution networks are set up to handle the AC voltages that we use in our homes. Magnetic storms induce DC currents in these networks.

Last modified prior to September, 2000 by the Windows Team

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