Merry and Bright

19 December 2019

Santa Claus doesn’t break his promises and neither do we! Hence, we are talking about alternating current (AC) and direct current (DC) today, as promised. If you missed last week’s blog, you’re in luck. Blogs are not holiday cookies - left out in the breakroom - scarfed down by the hungry office elves before 8:03 am. Blogs never get eaten. You can find last week’s right here. You’re welcome!

If you’re the grinch, this is not the blog for you because we’ve already thrown in three holiday references and the holly jolly goodness is just beginning. Just kidding, but one last one for good (holiday) measures… Let’s get this sleigh ride started! Okay, we’re done for now.

Anyways, both AC and DC are types of current flowing in a circuit. By the way, current is just the flow of electric charge. In direct current, electricity flows in one direction (directly); whereas, in alternating current, electric charge changes direction intermittently (or alternates). See what we did there? The name is literally the definition. Let’s break each of these down a little bit more.

Direct Current (DC)

As we discussed last week, America’s first power plant – owned and operated by Thomas Edison – ran on DC electricity. To generate direct current, you’ll need to use one of the following methods: a battery, a rectifier, or a commutator.

A chemical reaction inside of a battery generates DC; however, once the reaction is over, additional energy cannot be generated. Imagine taking a gallon of milk (after you set out a glass for Santa) and poking a hole near the bottom of the jug. The milk is going to come pouring out of that hole, until all of the milk is gone. Once it’s gone, it’s gone forever. It’s also not going to suddenly fly out of the top of the container either, it will simply flow in one direction. Are you catching on yet?

You can also use a rectifier or a commutator. A rectifier is an instrument that rectifies (or corrects) current by converting AC to DC – causing current to flow in one direction, rather than periodically switch back and forth. Many radio, television, and computer applications require DC, so rectifiers are used to supply power. Likewise, a commutator can be used to reverse the current direction, specifically for electric motors and generators – basically acting as a mechanical rectifier. A commutator will reverse the direction of current between a motor’s rotor and external circuit, producing torque, which converts alternating current from the windings to direct current in the external circuit.

So, what uses DC electricity? Anything that you plug into a wall with an AC adapter, connect to a USB cable, or power with a battery runs on direct current. We assume you can name quite a few electronics that fall into one of these categories, but just in case you are having a brain-freeze, this includes everything from your cell phone to the Tesla you’ve been begging Santa for. Ironic that the Tesla runs off Edison’s power source? Yes or yes?

Alternating Current (AC)

Now let’s talk about Tesla’s favorite current – AC. Alternating current is produced by an alternator, which is just the fancy word for an electrical generator that is specifically designed to produce AC. The name makes a lot of sense though, so we’ll let the engineers and their fancy naming schema go this time. If you were to crack open an alternator – not a recommendation – you would find a loop of wire, spinning inside of a magnetic field. As the wire spins around, a current is induced along the wire. Very exciting stuff.

There are a lot of things that can be used to spin that wire around, including: wind or steam turbines, running water, etc… Since the wire spins and the magnetic polarity is fluctuating, the voltage and current on the wire tends to ALTERNATE, as well. Hence, alternating current. Very simple, people. Now, I would love to make another holiday milk analogy for AC, like above, but it just doesn’t work, as well. Sometimes, less is more, so let’s just leave it like that. If you are really looking for an analogy, you can check out the water analogy here.

Alternating current is used to deliver power to homes and offices. When you see an outlet, it’s most likely an AC outlet, since AC is fairly simple to transport and generate across lengthy distances. If you send electricity at a high voltage (above 110 kV), you’ll lose less energy throughout the electrical power transmission process, which is great. Also, higher voltages indicate lower currents, which means less heat in the power lines. So many wins! If you want to transfer AC between voltages, then you’ll need a transformer. Substations and other electric facilities on the distribution grid are home to many transformers, for this reason.  

Are we done yet?

Well, you’re almost an AC/DC expert, but we can’t leave this until we at least mention the band, right? Did you know that AC/DC was named after the lead guitarist’s younger sister noticed the “AC/DC” initials on the back of her sewing machine? Very hard-core. Unfortunately, some argue that it was actually written on his sister-in-law’s vacuum. Either way, it was written on household appliance and “the name symbolized the band’s raw energy and power-driven performances,” according to the book, Rock Band Name Origins: The Stories of 240 Groups and Performers. So creative!

One last thing.

If you’re reading this and you happen to be an electrical engineer, electrician, or a particularly handy-man (or woman) interested in electricity, then you may want to add a voltage detector to your wish list too, if it’s not too late. From compact, pen-style instruments that identify the presence of live AC voltage to dual AC/DC voltage detectors with built in continuity and voltage measurement features, identifying voltage has never been easier – making your job simpler and your life safer.  

Before reading this blog, you probably had no idea that current could be so festive but based on the number of holiday references that we’ve made over the course of these 1,000+ words, I think we can all agree that it is indeed quite festive. Without current (and electricity), you wouldn't be able to deck the halls (and the outside of your home) with thousands of beautiful, bright lights each year. Besides, what is more merry and bright than electricity? 


Meredith Kenton, Digital Marketing Assistant, Valley Forge