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Why Are We Still Dependent on AC Current in a DC Dependent World?


Introduction to AC and DC Current

Electricity is a unique force of nature, known to only few species, such as the torpedo fish (Atlantic Coast), electric eel (South America), and electric ray (Pacific Coast). Most of us have witnessed its effects during a summer storm, or after dragging our shoes on the ground before reaching for a doorknob. Over the years, we have developed ways to harness this energy to power light, vehicles, and vast computer networks. As time has passed, technology has doubled its necessity and complexity, creating the abundant use of semiconductors and transistors (read more about semiconductors) to protect the vital guts of a circuit board. Without a rectifier to smooth out the bumpy ride of AC current, most of our technology would be fried by its raw power.

AC (Alternating Current) can be created by a rotating magnet along side a tightly wound coil. As the magnet approaches the coil, electrons are pushed forward. As it draws away, the electrons are pushed back out. The resulting configuration looks like a sine wave from an oscilloscope’s perspective, pushing the voltage to a positive peak, and then back down to a negative. DC current, by comparison, is the flow of electrons in one direction, either positive or negative, using a steady voltage. Anything from 1.5 volts to hundreds of volts can be supplied, but it will remain constant. Its singular direction makes it ideal for battery usage, considering it would be pointless to push negatively charged electrons into its body, only to pull them back out. If we need to achieve a DC-like current from an AC source, a one-way valve must be used, also known as a rectifier.

Why Would You Need to Use a Rectifier?

Most high tech electronic devices prefer clean, stable power. The problem with AC is it can be dirty, referring to its vast connections to electronic devices in neighboring cities, towns, subdivisions, and even your own electronic arsenal in your home. The result is a lot of noise hidden within its voltage. Most electronics cannot handle the positive and negative fluctuations of AC current, so a rectifier is used to inhibit the back flow of negatively charged electrons. Rectifiers only allow current to flow in one direction, much like the gate in a parking garage. A driver takes a ticket, pulls their car in, and the gate immediately drops down, inhibiting the possibility of getting back out from where they started. The only option is to move forward until the next exit opportunity unveils itself. The result is a constant, continuous flow of energy in one direction, which is imperative to keeping most electronic devices from damage.

In 1930, AC current was perfectly happy living in our refrigerators, ovens, and radios. However, In the 21st century, semiconductors have become pervasive in just about every form of technology we use. Semiconductors require a steady and controlled source of current to function properly. These types of circuits can be found in everything from digital refrigerators to simple light dimmers. In addition, anything with a digital clock requires a rectifier. Your digital camera, cell phone, laptop, and MP3 player all use sensitive circuits requiring the use of some sort of voltage rectifier. If you are wondering where such small devices can fit these components, they are often included inside the power brick, located along the cord that plugs into the wall. These are also known as a wall wart, referencing their annoying habit of blocking at least one other plug outlet.

It would be difficult to find any modern electronic device in your home that does not use some form of a solid state circuit rectifier. Perhaps one of the last remaining, truly AC components is the universal motor. We now have the perfect solution for taming AC current to be used with most DC devices. However, we also have to consider how the rectifier will be used, and the voltage requirements of the device. There are a lot of different materials that can be used for voltage rectification, which will be discussed next.

But Isn’t Rectification Wasteful?

When a modern society becomes acquainted with the battle between AC and DC current, also known as the war between Thomas Edison, Nikola Tesla, and George Westinghouse, it may at first seem wasteful to produce AC, only to rectify it to DC. After all, direct current does power the majority of electronic devices in our homes, and transforming AC to DC waste’s energy. Despite this fact, there are a number of advantages that AC has over DC.

AC can be used with a smaller gauge wire, which means it is ultimately less expensive. DC is more compact and has a cleaner output. However, AC is superior to pushing power where we need it. AC allows its voltage to be stepped up by a transformer (read more how transformers work) to travel over large distances (with minimal loss), and then stepped down to a useable power output once it reaches its destination. Transformers will not work on DC. They have to have AC power. So, in order to successfully transport power to your home, while also keeping it safe and usable for sensitive electronic devices, we need to rectify AC to DC.

In other words, we are going to be dependent on AC current, indefinitely. However, one of the ways we can make this system more efficient, is to place small DC substations in neighborhoods and business districts. What this would accomplish is to reduce the necessity of AC rectifying (adapter) components in electronic gadgets, allowing them to function with greater efficiency, which also means less heat. We may be a few decades out from this type of idea taking hold, but it is at least one alternative to the race to find more efficient ways to bring power to your home.



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