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Difference Between AC and DC Electricity


We use electricity so often in our lives that we tend to forget that there is more than one form in nature: There is the AC (Alternating Current) and the DC (Direct Current). These two forms, while both being basically electrical currents, have many differences in how they behave and function. This is particularly important to know because of the specific applications that both types of electrical current are best suited for. With the concerns about power that prevail in our world today, it would be best for everyone to understand what the differences between AC and DC are.

Alternating Current (AC) is the more common form in our modern world. The electricity that our homes, offices, schools, and other establishments receive from the power plants is in the form of AC. The reason for this is that AC electricity can be transmitted efficiently which facilitates the transfer from the source (i.e. the power grid) to the consumer (like your homes, for example). Compared to the early years when electricity was only becoming a household necessity, modern homes and establishments often receive more power than they actually consume.

The term ‘Alternating Current’ came from the simple fact that the current reverses at certain intervals, i.e. it changes ‘direction’ when it flows. This interval varies depending on your location and the needs of the area. For instance, the US has different intervals for the AC traveling through power lines than countries in Europe or Asia. The range of frequency is either 50 or 60 Hz and in some countries, like Japan, both are used. To further illustrate, the local power plant could put out a few million volts of AC electricity through power lines; once this power reaches the area for consumption, then the principle of using transformers come into play. A transformer can be used to increase or decrease the amount of electrical output, although more often the latter is used for safe consumption. The power would be converted to a lower voltage and when it finally reaches your homes, the wall socket would probably have an output of a hundred volts or so.

On the other end, you have Direct Current (DC); it was also widely known as galvanic current in its early applications. As one would suspect, DC electricity does not constantly change. This type of current flows in one direction and no change occurs in how it flows. Your common battery is an example of a device that produces DC electricity. Solar cells and car batteries are also common examples. Remember the two ends of the battery? There’s a positive and a negative, right? Those are indications of DC electricity as they don’t change flow; positive remains positive and vice versa.

In the early 19th century, DC electricity was the form used to provide power in the US; however, DC electricity had the flaw of losing power after traveling a certain distance, roughly a mile or so. It was during the latter part of this century that AC electricity became the ideal and preferred form used to distribute large amounts of power over great distances. However, recent developments in technology make it possible and practical to distribute and use DC electricity in the same manner as AC electricity.

Because of the nature of certain devices and appliances, means to transform AC to DC are available, particularly in this day and age. For example, laptops typically use batteries as their primary source of electricity. With an adaptor plugged in, it transforms the AC from wall sockets that your DC battery can use to power the laptop and charge itself up. DC to AC conversion is less common; the most common use of this is in automobiles. The battery is DC and an alternator transforms it into AC which is in turn distributed as DC throughout the car’s systems.


1. Alternating Current (AC) refers to electrical power that constantly changes flow at intervals or depending on its use. Direct Current (DC) refers to electrical power that flows in a unilateral direction and is often characterized by a positive and negative end.
2. AC is more efficient for distribution across long distances without losing power, as in the case of power plants. DC is preferred for smaller items or isolated distribution such as batteries and solar cells.
3. AC can be transformed to DC, and vice versa through the use of adaptors, depending on the needs of the device.

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  1. Great article. I am researching information on Solar panels. Some companies use DC electricity and others use AC. Still trying to find out what’s more beneficial and practical for solar panels.

  2. Hello

    I’m not sure if this is right in the article: “The battery is DC and an alternator transforms it into AC which is in turn distributed as DC throughout the car’s systems.”

    The alternator does not convert the DC from the battery to AC. The alternator produces AC which is converted with a converter to DC to charge the battery.

    DC to AC is used for example for solar panels which produces DC and then a converter converts it from 12V DC to 110/220V 50HZ/60HZ AC that it can be used for home.

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