The War of the Currents

In this chapter, we focused mainly on what is called direct current, or DC, electricity. This is the kind of electricity that comes out of a battery—when you turn a 5 V battery on, you get 5 V all the time until the battery runs out of juice. This is not, however, what comes out of the wall. The electrical grid uses alternating current (or AC) electricity. Additionaly, the voltage that comes out of the wall is a sinusoid that varies (in the U.S., at least) from +120 V to -120 V at a frequency of sixty times per second.

Why it's AC (and not DC) power that comes out of the wall was a huge debate when the electrical grid was being created. The groundwork for the U.S.'s electrical infrastructure was laid in the late nineteenth century, the "Age of Great Inventions," when railroad tycoons and oil barons and steel magnates were transforming post-Civil War America into the modern country that exists today. An integral part of that transformation was the delivery of electricity to every home in the nation.

The AC and DC camps fought long and hard. In one corner, weighing in at one-hundred-eighty-three pounds, we had the Perspiring Power Pioneer, the Man of a Thousand Patents, the Wizard of Menlo Park—Mr. Thomas. Alva. EDISOOOOOOON!

And in the opposite corner, the challenger, weighing in at one-hundred-forty-two pounds: the Westinghouse Powerhouse, the Scintillating Serbian Scientist, the Eclectic Electric Eccentric—Mr. Nikola. TESLAAAAAAAA!

The power pugilists had very different visions for how electricity should flow throughout the country. Edison championed DC power, which he had popularized after inventing the light bulb. DC electricity is difficult to transmit over long distances, however, and so Edison hired a young engineer named Nikola Tesla to come up with a better solution. Tesla (who was a cool enough guy that, not only did he have a car company named after him, but he was portrayed by the one and only David Bowie in a major Hollywood film) came back to Edison with the idea of AC electricity, but Edison believed the idea to be impossible to implement.¹⁴ An industrialist named George Westinghouse came to Tesla's rescue, licensing his AC power patents and diving into the utilities market. And so, with a shock heard round the world, the opening salvos of the War of the Currents were fired.

While Edison was a great inventor, the AC power turning on all the lights in your house right now should tip you off that Tesla was the one who was right. AC electricity is much easier to "step up" to higher voltages using a device called a transformer. A transformer generally consists of two coils of wire, one with far more coils than the other. A constantly changing current (like AC electricity) is sent through the small coil, which creates a magnetic field according to Faraday's Law. This magnetic field creates a voltage in the larger coil, which is proportional to the number of loops in the coil—creating a much larger voltage than originally present. Because of conservation of energy (pesky, we know), the amount of power must remain constant, so a stepped-up voltage will be accompanied by much lower current. P = IV is always the same.

Long electricity lines are plagued by the build up of a large resistance over the length of the wire, which drains off power like a mynock. The power loss across a wire due to its resistance is P = I²R—the more current, the more power is lost. Because of this, high-voltage, low-current AC power is much more efficient than low-voltage, high-current DC power when sent along long wires, and that means it's much cheaper.

AC power can then be stepped-down using a transformer with the coils reversed and sent into homes to power lights and toasters and washing machines and whatever else you plug into the wall. Transformers won't work for DC power since the crux of a transformer is Faraday's Law. Faraday's Law relies on changing magnetic fields to create voltages. The big benefit of DC power is that it never, ever changes, making electromagnetic induction impossible.

Edison may have realized this, but resolutely refused to give up. He launched a massive smear campaign against Westinghouse and Tesla, electrocuting dogs and cats (and, in at least one instance, an elephant) with AC power to prove how dangerous it was. He went as far as ensuring the first electric chair used for capital punishment was furnished with a Westinghouse AC dynamo.

Yet it was Westinghouse who got the contract to power the 1893 Chicago World's Fair, arguably ushering in the era of electricity.¹⁵ There are advantages to DC power—DC electricity needs less wiring to transmit, for example, and those boxes on the power cords of your computer or cell phone chargers are AC-to-DC converters, since those devices all run on DC power. However, the low cost of transmitting AC power from point-of-generation to point-of-use eventually won the war.