Alternating Current

Alternating Current            

         AC is short for alternating current. This means that the direction of current flowing in a circuit is constantly being reversed back and forth. This is done with any type of AC current/voltage source.

        The electrical current in your house is alternating current. This comes from power plants that are operated by the electric company. Those big wires you see stretching across the countryside are carrying AC current from the power plants to the loads, which are in our homes and businesses. The direction of current is switching back and forth 60 times each second.



  Electrons alternate directions in AC electricity


With an AC generator, a slightly different configuration alternates the push and pull of each generator terminal. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position.


This illustration gives an idea of how the electrons move through a wire in AC electricity. Of course, both ends of the wire extend to the AC generator or source of power.

AC movement of electrons in wire

       The charge at the ends of the wire alternates between negative (−) and positive (+). If the charge is negative (−), that pushes the negatively charged electrons away from that terminal. If the charge is positive (+), the electrons are attracted in that direction.

Advantages of AC electricity

      There are distinct advantages of AC over DC electricity. The ability to readily transform voltages is the main reason we use AC instead of DC in our homes.

Transforming voltages

     The major advantage that AC electricity has over DC electricity is that AC voltages can be readily transformed to higher or lower voltage levels, while it is difficult to do that with DC voltages.
     Since high voltages are more effecient for sending electricity great distances, AC electricity has an advantage over DC. This is because the high voltages from the power station can be easily reduced to a safer voltage for use in the house.
     Changing voltages is done by the use of a transformer. This device uses properties of AC electromagnets to change the voltages.

(See AC Transformers for more information.)

Tuning circuits

     AC electricity also allows for the use of a capacitor and inductor within an electrical or electronic circuit. These devices can affect the way the alternating current passes through a circuit. They are only effective with AC electricity.
     A combination of a capacitor, inductor and resistor is used as a tuner in radios and televisions. Without those devices, tuning to different stations would be very difficult.

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