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AC & DC current

There are two types of electrical currents that can flow through wires: direct current (DC) and alternating current (AC).

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. 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. So any single electron takes a long time to get all the way around the circuit. 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.

        Alternating Electricity (AC) is generated when a coil of wire moves in a magnetic field.
 This is the basis of electricity generators.
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, since the same amount of current flows through a circuit regardless of the direction of the current.

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An  AC generator requires a coil to cut across the force lines of a magnetic field. This coil is attached to two slip rings, which deliver the current to and from the load destination, thus completing the circuit. Alternating current generators are often called alternators.

During the first half turn, the coil cuts across the field near the magnet's north pole.  Electrons travel up the wire, and the lower slip ring becomes positively charged. When the coil cuts near the South Pole of the wire  during the second half turn, the lower slip ring becomes negatively charged, and electrons move down the wire. The faster the coil turns,                    the faster the electrons move, increasing the frequency (in Hertz) of the current produced by the generator.

Click on the picture to observe the relation between the voltage and the time as we increase and decrease the frequency 
AC current

Difference between AC and DC:
1 - Alternating current is the best way to transmit electricity over large distances.
2 - AC can even be changed to DC by an adapter that you might use to power the battery on your laptop or your mobile or battery charging, radios, televisions. The DC cannot be converted AC.
3- While DC can be stored in batteries, you cannot store AC.
 4- It is better to use AC if the potential difference required is not the same as the supply voltage e.g. low voltage lamps.
5- The AC voltage can be increased or decreased by a transformer or an adapter.


Videos to summarize the AC and DC electricity: