In the July/August issue of Home School Enrichment, we did an article entitled "The ‘Shocking' Story of the Battery." A battery is a device that provides electricity in a form called direct current. While batteries are useful for many applications, they have a problem: the direct current they provide cannot be transmitted over long distances (like miles) to provide power to homes and businesses. The invention of alternating current changed that. The way alternating current works makes it very efficient for distribution over power lines.

The World Before Alternating Current

The phenomenon that we know as electricity was first observed about 2750 BC. Ancient Egyptians were familiar with a fish that could shock people. They called it "the Thunderer of the Nile." There are, in fact, a number of fish that can produce electrical shocks, and believe it or not, they were the first electric "devices" people tried to use to alleviate symptoms such as headaches. Sick people were told to touch electric catfish and rays in hopes that the electric jolt would help heal them!

Early scientists, such as Thales, discovered that if a material called amber was rubbed with a piece of cloth, small bits of straw would stick to it. It was as if some mysterious power had been unleashed in the amber. Today, we know that mysterious power as static electricity, and many of us have felt the jolt from a static shock as we walked across carpet.

It took many years, centuries in fact, before scientists began to understand the fundamental properties of electricity, what it was, and how it could be used as a source of energy. In the late 1800s scientists began to invent devices which could actually use electricity to do some useful function, such as the lighbulb, which could supply illumination. But a war was beginning to brew: the War of the Currents.

Static electricity provides a steady stream of particles, called electrons, that move in one direction. The stream of particles, like a stream of water, is called a "current," and the single direction that the electrons flow is called "direct current," or DC. Batteries supply DC. Inventor Thomas Edison was a proponent of using DC to power his inventions.

Other scientists, particularly those in Europe, had found that they could use rotary motion to move magnets to produce oscillating currents. With these currents, the flow of electrons alternated in the direction they moved. This alternating current is known as AC.

In 1882, the first electrical power distribution system was turned on, providing 110 volts DC to some 59 customers located near Thomas Edison's laboratory in lower Manhattan. Engineer, inventor, and entrepreneur George Westinghouse became interested in electricity, but he had some concerns that Edison's DC system was not very efficient. Edison's system used low voltages, but required high currents. This resulted in significant power losses. There was also another serious problem. Different devices, such as lights and motors, required different DC voltages, which meant different electrical lines had to be run to supply the correct voltage level to each piece of equipment.

Westinghouse was aware that a number of Europeans had been experimenting with the novel concept called AC. Alternating current had the advantage that the voltage could be "stepped up" (which means increased) for transmitting over long distances without a power loss, then "stepped down" (which means decreased) so it could be used by consumers. Edison's DC system could not do this.

The Invention of Alternating Current

In 1886, George Westinghouse and some of his colleagues installed the first AC transmission system in Barrington, Massachusetts. A generator produced 500 volts AC and "stepped it up," using a transformer, to 3000 volts AC. The high voltage was transmitted across the power lines and then "stepped down," using another transformer, to 100 volts AC, the voltage used to operate lights.