The Difference Between AC and DC Electricity



Let’s talk about DC versus AC electricity, the difference between them, and some pros and cons of each. DC stands for direct current, which is easy to remember that the current is flowing directly from one point to another. With DC, the current flows in a loop from a higher voltage to a lower voltage, before being pumped back up either with a battery or some other type of power supply.

Physically what happens with DC is that the battery or power supply is forcing more electrons to one side of the circuit either with a chemical or electrical process, trying to maintain the voltage.

AC, or alternating current, is when the current changes direction as the polarity of the voltage changes. You will sometimes see the voltage being represented as a sine wave with it moving from positive to negative while also momentarily not having any voltage differential. This changing voltage corresponds to the electrons flowing first one direction, and then another. As the current is still going through a load, it’s still doing work and requires power. Usually, when you think of AC power, you think of what comes out of the wall outlet, which is typically 60 or 50 hertz, meaning it goes through an entire cycle 60 or 50 times a second. For old incandescent light bulbs, this means they, ideally, flicker faster than our eyes can see.

Why we use DC versus AC

DC is very simple. Easy to make, easy to use. Most electronics devices use a DC power supply. You can carry it around as small batteries or even capacitors, and at really high voltages, is actually better for long distance transmission because it doesn’t suffer from the skin effect that plagues AC circuits. At the same time, even though it’s easier now than it was a hundred years ago, it’s still pretty hard and expensive to change the voltage of a DC signal. It’s also difficult to create a good AC signal from DC power - most DC to AC inverters fake it by creating a square wave instead of a sine wave.

AC is much easier to increase or decrease voltage with simple and low-cost transformers, which means you can change the voltage for long distance power transmission, something we’ll talk about more in a later video on power. AC can be easily generated mechanically such as with a generator and changing AC to DC is a straightforward and efficient process. Which is good because AC doesn’t work with many things naturally other than items with motors or incandescent lights. It’s also not as portable, which means that if you need AC power away from an established power grid, it’s going to be a real pain. So, there are pros and cons with both.

In summary:

  • AC / DC
  • Benefits / Drawbacks
  • DC is easier to use
  • AC is easier to transport

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