What Is Alternating Current?

By Megan Tung

Alternating Current (AC) is when the electric charge changes direction periodically. As a comparison, direct current (DC) is when electric charge only flows in one direction. In the US, the direction of the current reverses/alternates at 60 Hertz (cycles/second). The most common waveform with AC is a sine wave; although, square and triangle waves are other waveforms for AC.

Alternating Current What is It

A special type of electrical generator, called an alternator, is designed to produce the alternating current. How an alternator works is there are rotating magnets known as the rotor and the conductor wound in coils on an iron core called the stator. When the stator makes a complete rotation, an electromotive force in the form of current is induced in the stator, producing the AC voltage. AC power is used to deliver power to houses, office buildings, etc. AC power can also be used to power electric motors, such as dishwashers and refrigerators.

Alternator Operation How it Works

Generating and transporting AC across long distances is relatively easy. Power companies send very high voltages to be able to transmit the power over long distances. AC can be converted to and from high voltages easily through the use of transformers. Multiple transformers are used to safely get the right amount of AC power from power plants to houses.

First, electricity is generated with huge generators either by wind, coal, natural gas, or water. Next, the AC goes through transformers to increase the voltage to allow the power to travel long distances. The electrical charge flows through high-voltage transmission lines. Then it reaches a substation, where the voltage is lowered so it can be sent on smaller power lines. The charge travels through distribution lines to a neighborhood where smaller transformers reduce the voltage again to make the power safe for using in homes. The power is then connected to the house where it passes through a meter that measures how much power the household uses. The current goes through a service panel, where breakers/fuses protect the wires from becoming overloaded. The electricity then travels through wires to the outlets and switches in the home.

Transporting Electricity How it Works

Some devices will require an AC adaptor, which will use another transformer to convert the electric currents received by the electrical outlet into a lower alternating current that an electronic device can use. The number of transformers the current has to go through depends on the maximum amount of current the electronic device can handle.

Your may also be interested in reading: How a Transformer Works
Megan Tung is a summer intern at Jameco Electronics, attending the University of California, Santa Barbara (UCSB). Her interests include photography, music, business, and engineering.

Photo Credits: Solar Schools