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Published on
April 12th, 2021

The More You Know: AC vs. DC Electricity

You probably see the words AC or DC power virtually every day without thinking about their meaning. But it’s helpful to know the difference between AC vs. DC electricity and why both types of power are still in use. Here’s a quick science refresher on the two, so you understand how they work when it comes to the electrical wiring in your property and the use of electric devices in your daily life.

AC vs. DC Electricity: What’s the Difference?

Alternating current vs. direct current

AC power stands for alternating current. This is the type of electricity that emanates from the power outlets in our homes and businesses. It’s called “alternating” because the current periodically reverses direction.

On a subatomic level, this change in direction is referring to the flow of electrons. Electrons are negatively charged particles found in all atoms. If you were to graph the flow of alternating current, it would look like a wave or sinusoidal pattern. The up side of the curve is the current flowing in a positive direction, while the down side is the current moving in a negative direction, giving it an oscillating pattern.

Conversely, DC power, which is short for direct current power, moves in only one direction. It is a constant, forward movement of electrons, not an alternating pattern. If direct current electricity were represented on a graph, it would resemble a flat line.

It is difficult to get direct current power to travel long distances, such as from a power plant to a house. This is why it’s used in other applications (see below), but it’s not used to power the electricity we receive from our outlets. The wave-like motion of alternating current power, on the other hand, turns out to be very efficient, which is why we have AC power as our standard in contemporary everyday structures.

A Brief History of AC vs. DC Electricity

A long-standing rivalry

In the late 1800s, people were still using candles and gas lamps for light. There was no electrical utility as there is today. But in 1879, Thomas Edison’s invention of the incandescent light bulb changed everything.

Edison envisioned a world where homes and businesses would have light powered by electricity. Because his light bulbs ran on direct current electricity, he set up an experiment in New York City to power a segment of the city by using huge dynamos that called on steam engines to convert energy to the electricity he needed. Edison Electric, which eventually became General Electric, was founded, and several of his power stations were built in Manhattan.

The problem with Edison’s electrical power is touched on above: because DC power is inefficient and can only travel a short distance, power stations needed to be quite close to the buildings they were supplying. This ate up a good deal of priceless real estate in New York City. Furthermore, only urban areas were able to receive power, while rural locations had nothing.

Along came Nikola Tesla, a Serbian-American inventor, who actually worked for Edison for a time. He developed a motor to generate alternating current by spinning a magnet inside a wire coil. In addition to this alternator, Tesla invented transformers that could modify the voltage of the electricity produced. A high voltage could be generated at power stations and then lowered to safer levels near homes and businesses.

Edison, however, was still attached to his concept of DC power and refused to implement Tesla’s designs. Tesla decided to pursue them on his own and obtained patents that were soon purchased by George Westinghouse, the famous founder of Westinghouse Electric Company.

The “War of the Currents” was on. Edison tried to prove AC electricity was too dangerous for everyday use. Nevertheless, Tesla won the contract to supply power for the 1893 Chicago World’s Fair. Once George Westinghouse set up an AC generator that used Niagara Falls to power electricity for the nearby city of Buffalo, AC power was on its way to becoming the national standard.

Why We Still Need Both Power Types

AC vs. DC electricity in daily life

Today, of course, AC power is what emanates from the power grid to our electrical outlets. Our appliances, from toasters to washing machines, all use AC power.

But what about DC power? That too is still in use but in different ways than how Edison originally envisioned.

Solar panels, for example, produce DC electricity. In order to harness that electricity for your own use or to sell it to the grid, it must first be converted to AC power via an inverter. An inverter employs transistors that switch on and off very rapidly to direct electricity along multiple paths and change its direction.

Batteries are another source of DC power, which is much easier to store than its AC counterpart. And electronic devices, like televisions, cell phones, and computers, don’t like the minute losses of power that accompany the changes in direction that occur with an alternating current. Therefore, they use power adapters that transform AC power from wall outlets to DC power for the device itself. Adapters contain diodes that change the current to one direction only, getting rid of the fluctuations that come with AC electricity.

Because DC electricity is so widely used outside of the power grid, new research is looking for ways to make direct current electricity travel further, so the step involving conversion from AC power can be eliminated. Green energy and electric vehicles are some of the forces driving innovation in DC electricity today.

Whether you’re installing charging ports for electric vehicles on your property or simply want to upgrade your AC electrical panel, Bolt Electric should be your electrician of choice. We’re New York City’s hyper-local blue-chip electrical experts. Call us at 212-434-0098, or use our online form to schedule an appointment at a time convenient for you.

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