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Understanding Alternating Current (AC) vs. Direct Current (DC) – Which is Better?

11 Aug 16
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What is the main difference between AC or alternating current and DC or direct current?
Based on its name, direct current is an electric current travelling in just a single direction as compared to alternating current that occasionally reverses direction. Negative and positive poles in an electric or magnetic field create a condition wherein electrons flow, known as polarity. Direct current system has fixed polarity where a single pole is positive all the time while the other is negative at all times.

On the other hand, an alternating current continuously reverses polarity at a rate that is identified by its frequency. This frequency is being measured in terms of Hz or hertz that is equal to a single cycle per second. In the United States, they make use of 60 Hz while 50 Hz is used in Europe. For instance, Japan uses both, with the western half using 60 Hz and the eastern half makes use of 50 Hz. Majority of today’s appliances are being manufactured in order to accommodate the two frequencies.
During the late 1880s when modern electricity started being produced on commercial scale, there was a fierce rivalry that ensued between AC supporters and DC supporters, which is referred to as the War of Currents. Thomas Edison himself was a staunch advocate of DC while George Westinghouse, with the backing of Nikola Tesla promoted AC.

Why Alternating Current Dominated the War of Currents
At the time, it was clear that alternating current was much superior when it comes to transmission of large electricity amounts over large distance mainly because of its ability of easily stepping the voltage up and down. When electricity travels up and down the conductor, it will lose its energy in heat form because of resistance as expressed by Joule’s first law.

It means that energy tends to be lost in proportion to the current. An obvious solution for this was to increase the voltage to reduce the current – higher voltage will equal the ability of lowering the current for similar power. However, it became crucial to transform the voltage both prior and after the long distance lines when distributing it to consumers.

Back then, the issue with direct current was that there was still no viable means of doing this while it was much easier to do so with alternating current. In today’s world, technology became more advanced in which not only is long distance DC viable but there are even instances when it is far more superior than AC in the form of HVDC or high voltage direct current.

Benefits of Direct Current

• DC is about 1.4 times more efficient since it is not a sine wave.
• DC doesn’t lose power to the reactive losses. These reactive losses are the ones suffered by AC lines through heat because of the natural capacitance of the conductive material as well as the back and forth motion of AC.

Benefits of Alternating Current

• Easier and cheaper to transform voltage.
• Due to the alternating current, plugs can be easily inserted in direction as compared to DC that needs one prong bigger than the other to guarantee proper circuit.

Bottom Line
In light of modern technology, alternating current systems are much more economic for the short distances. AC has the benefit of cheaper transformers and DC, on the other hand, has the benefit of cheaper insulators and wire, making it the winner as far as long distances are concerned.

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