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# 5. The Difference Between AC and DC Power (A Look at Electricity From Alternating Current vs Direct Current)

What Is the Difference Between AC Power and DC Power?

Prerequisite

Before you can understand the difference between AC and DC, you might want to read my very short, easy-to-read article: What Is an Electric Circuit?

Then, come back to EASILY understand the bare-bone basics about AC and DC power.

There are two types of electrical power: alternating current (usually called “AC”) and direct current (usually called “DC”).

In the United States, our homes are powered by alternating currents (AC). But what exactly is AC power, and how is it different from direct current (DC)?

To learn about the differences between AC and DC power, let’s first take a look at each of them separately.

## Direct Current (DC)

DC (the direct current) is an electrical current that constantly moves in a single direction across the electrical circuit, from negative to positive.

An example of a DC power source is a 12-volt battery, which has a negative terminal and a positive terminal.

When you attach two wires to the positive and negative terminals of the battery, and you connect it to an appliance that is rated for 12 volts (like the 12-volt mini-fridge in the picture), the electrical force/charge will flow through these wires, from one side of the battery (negative) to the appliance, and then will flow out of the appliance back to the battery (positive).

You can think of the DC current like a river. The electrical force flow through the whole thing but can only go one way.

When you measure a DC voltage with a digital meter, the reading will be either entirely positive or entirely negative.

## Alternating Current (AC)

AC (the alternating current) is different than DC in that the electrical signal changes from positive to negative really fast and this causes the electrical force/charge to vibrate instead of flowing like a one-way river, like the DC current.

When I say “vibrate”, I don’t mean that the wires, battery, or appliances actually vibrate. It’s not a physical vibration. It’s the electrical force inside the wires that move back and forth at a regular speed (the technical term for this is oscillation).

In the United States, the electricity in an AC current switches back and forth 60 times per second.

In an AC system, there is no polarity (no positive or negative).

Is House Electricity AC or DC?

We all know that electricity is what powers our homes, but is the electricity coming out from the outlets AC or DC?

Most of the time, the electricity coming from outlets in a house is AC.

Why DC Is Not Used in Homes

So why do our homes typically use AC instead of DC? The answer has to do with efficiency.

AC is more efficient than DC for long-distance transmission because it can be transmitted at higher voltages, which reduces energy losses due to resistance in the wires. That’s why AC is the choice for power grids and long-distance transmission.

Is AC Power Better Than DC?

In the early days of electricity, there was a battle between those who advocated for using alternating current (AC) and those who preferred direct current (DC).

While both have their pros and cons, AC is now the standard for electrical power.

One of the key advantages of AC over DC is that it can be easily transformed to different voltages. This is important because different devices require different voltages to operate correctly. For example, a small appliance might need 110 volts while a large appliance might need 220 volts. With DC, transforming the voltage is difficult and expensive.

And, as we previously discussed, another main advantage of AC is that it can be transmitted over long distances without significant loss of power. This is because AC can be generated at high voltages, which are then reduced to lower voltages before being used in homes and businesses.

On the other hand, DC power is much easier to store and transport than AC power. This is because DC power can be stored in batteries, while AC power must be transported through wires. This makes DC power much more convenient for use in portable devices and for powering remote locations.

People like me who are living off-grid rely heavily on DC power. This is because solar power systems create DC power from solar panels and then that power is stored in batteries for later use.

So there is a need for both AC and DC power. In the end, it is up to the user to decide which type of power is best for their needs.

Here’s a video that explains in more detail the importance of both AC and DC.

Overview: AC vs DC

In a nutshell, AC (which stands for alternating current) and DC (which stands for direct current) are two types of electrical power. AC is normally the type of power that comes from your wall outlets at home, while DC is the type of power that comes from batteries.

AC power is current that alternates, which means that the current reverses direction periodically. DC power is direct current, which means that the current flows in one direction only.

Both have their own advantages and disadvantages. AC power is more efficient and can be transmitted over longer distances, but DC is great for solar systems or for devices that run on batteries.

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