What Is an AC Circuit?
If you're just beginning your study of electrical circuits, you've probably become familiar with direct current (DC) circuits such as those created using battery power. While DC is straightforward and can help one grasp the basics of electrical circuitry, AC circuits are also extremely important and provide much of the power that we rely on each day.
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Identification
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AC stands for alternating current and an AC circuit is one in which the current alternates direction while the polarity of the power source reverses.
Considerations
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To understand an AC circuit, it's best to first consider a DC circuit. In a DC circuit a power source such as a battery creates a voltage that pushes current through a circuit. Electrons flow from the battery's negative terminal to its positive terminal, while powering an object like a light bulb. They flow in this same direction the entire time and the battery's positive and negative terminals are fixed. In an AC circuit, the voltage terminals reverse polarity and the electrons flow in both directions depending upon the polarity of the power source at a given time. Like a DC circuit, the electron flow powers a load (electrical device).
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Significance
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An AC circuit's voltage and current are constantly fluctuating. The fluctuations are depicted in the form of a sine wave. Since the sine wave is used to measure AC, wave measurements are used to denote AC circuits. Frequency is the number of wave cycles in a given amount of time and Hertz (Hz) is cycles per second. In North America, the power supply used for your home is 60 Hz.
Function
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AC power is created by an AC generator or alternator. An AC generator is an electromagnetic device with a rotary electric coil. As the electric coil rotates in a magnetic field, the opposite polarities of the magnetic field on either side of the coil cause electrons to flow in opposite directions and the polarity of the two terminals of the coil reverses. Since electrons flow from negative to positive, alternating current is created because of the shifting polarities.
Benefits
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While an AC circuit may sound confusing and difficult to use, there is one main reason that it is used for supplying power. AC allows alteration of voltage levels using transformers. Resistance is a property of any material that limits the flow of electrons. While conductors like copper wire have a low resistance and are efficient electron transmitters, resistance increases drastically over a great length of wire. In order to deliver electricity across distance, a high voltage level is needed to push the current and fight resistance. However, this high voltage would be dangerous if it remained constant when delivered to your home. Transformers are used to adjust the voltage levels as needed to send power out and supply power safely in a home or business. In short, AC power allows for voltage conversions that transport electricity efficiently and inexpensively, something that DC cannot do.
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