subject: Alternating Current (ac) Vs. Direct Current (dc) And Electricity [print this page] . Indeed, that wasn't always the case. The development of the incandescent light bulb in the latter half of the nineteenth century provided a meaningful reason for municipalities to trade in dangerous and dim gas light for brighter, more easily controlled electric light. (Some very old houses are still equipped with the plumbing that once carried natural gas to wall-mounted lighting fixtures.)
While it was always inevitable that electricity would be the fuel for the twentieth century, there was one big dispute that needed to be resolved before work could begin in earnest: whether the American power grid should be run with alternating current (AC) or direct current (DC). This dispute was not only a scientific one; big personalities were involved in what became an interesting chapter in American cultural and industrial history.
First of all, what are direct and alternating current? In a way, you already know the difference. All of the battery-powered devices in your life run on DC. The current (speedy electrons) invariably flow from the positive terminal of the battery, through the device and back into the battery through the negative terminal. The voltage never varies. When you use AC, on the other hand, the current oscillates between the power consumer and the power source. This is what makes the current "alternating."
There are advantages to using direct current, as the system is less complicated and can be packed in a smaller place. That's why your cell phone is much better suited to DC. Unfortunately, DC decreases as it's transferred over large distances. Alternating current reverses, buzzes back to the power plant with a regular rhythm. In the United States, this happens 60 times each second. This may seem fantastic, but you have to consider what's being transported. Electrons, you'll recall are the smallest part of an atom, particles with a negative charge. Because of their miniscule weight, it's possible for them to move that fast along the power lines.
Alternating current is also easier to distribute. It's efficient for power companies to transfer energy in bulk and at higher voltages. This, however, would not be safe for household use. The power goes to transformers that downgrade the power to the standard 120 volts (This number varies, depending on which country you are in.).
Thomas Alva Edison, the New Jersey inventor, had gotten a head start with his creation of an electrical grid. According to PBS's The American Experience, in 1887, Edison had already built 121 power stations. The problem was the distance restrictions imposed by direct current; a home more than a mile away from a power station would not get a full measure of power. Direct current got that far, as so many suboptimal ideas do, because of the power of Edison's name.
Other scientists were working on power grids of their own. People such as Nikolai Tesla were hoping that their work would lead to the standards for the American grid. A public relations war quickly ensued. Even though AC was demonstrably better than DC, Edison wanted to ensure that DC remained the standard. He began to attack Tesla's AC generator and the whole idea of alternating current. He once said, "Direct current is like a river flowing peacefully to sea, while alternating current is like a torrent rushing violently over a precipice."
It's true that all kinds of electricity are dangerous, but AC and DC have slightly different properties. An inadvertent shock of direct current, for example, may have been less harmful than one from an AC source, as there was no degradation of voltage in the latter. Edison, however, was engaging in some interesting public relations campaigns. Hoping to convince people that AC was more dangerous than DC, he paid for public electrocutions of animals using AC-generated power. Those in the audience must certainly have felt the desired effect: suspicion of alternating current.
At the time, those in the American justice system were also looking for more humane ways to carry out the execution of inmates. One of the solutions was what we know as the "electric chair," in which the condemned is restrained and electrocuted through electrodes applied to his or her body. According to PBS, a professor named Harold Brown tried to demonstrate the danger by carrying out one of these sentences using an illegally purchased AC generator. Brown and Edison's efforts worked, at least to an extent; this form of punishment was soon called "Westinghousing," named for the man who purchased Tesla's generator and ideas.
In the end, of course, the better technology won out and the United States adopted alternating current as its electrical standard, paving the way for electrification of rural areas and the standard of living we enjoy today.
