A junior majoring in Biomedical Engineering in Spring 2008, Robin was perplexed by the number of different types of electrical outlets she saw during her travels around Europe. She believed that there must be a way to standardize the outlet, though was unsure the international electrical outlet market would agree.

The electrical outlet is a modern convenience that we often take for granted – until it becomes an inconvenience. When traveling abroad, you must purchase adapters, converters and transformers with no guarantee that these will fit into your hotel room outlet. There have been a number of developments to make the outlet a safer, more user-friendly innovation relative to its origins of do-it-yourself wiring and light-bulb socket plugs. Its history is intertwined with that of modern household lighting and electricity. There has been little recent development in the electrical outlet, but there seems to be broadband internet in its future. Introduction When traveling abroad, you buy at least five different types of electrical adapters and transformers yet somehow still end up in a hotel where your cell phone charger will not plug into the outlet. Or, perhaps you have attempted to plug your hair dryer into the bathroom outlet using a simple adapter and have blown a fuse. Why do we need all these adapters and transformers while traveling? The simple answer is that individual regions independently chose to develop their own technology and no standard was set early on (Fig. 1 shows the US standard outlet). The electrical outlet is an invention created purely for convenience, so we tend to forget about its elegant engineering until it becomes an inconvenience. The engineering of the outlet has evolved: we have gone from about ten different frequencies to just two in the world, and we have two standard voltages as well. But where exactly did household electricity begin and how did it bring about one of the most over-looked, yet important, inventions of the modern household? AndrewBuck/Wikimedia​ Commons The History of Electricity There was considerable delay between the discovery of electric power and the capacity to harness this power for work; this transition is recorded in a series of biographies from Benjamin Franklin to Philip F. Labre. However, Ben Franklin did not “discover” electricity as so many of us are led to believe in elementary school history classes. In fact, the Greeks made early observations of magnetism and even wondered about the origins of lightning [1]. Lightning, as we now know, is caused by a buildup of electrons in thunderclouds when particles in the clouds rub together. As the electrons build up, they must discharge to a positively charged or neutral surface, usually another cloud or the ground. In the mid 1600’s, Otto Von Guericke created the first static electricity generator from a ball of sulfur [2]. This sulfur ball led to a century’s worth of investigation in static electricity. With his famous kite experiment, Ben Franklin proved that lightning was, in fact, a form of electricity : the same kind of “electric fire” was ejected from the kite as was produced by experiments similar to the one created by Von Guericke’s sulfur ball [3]. From this and other experiments, Franklin was able to develop his Electric Fluid Model. Franklin’s Model described electricity as a fluid and introduced the concept of “conservation” of “electric fluid” [4]. Within a system, however, charge can collect on one object and deplete on another, inducing “positive” and “negative charge, respectively. Fluid in this case does not mean a liquid, but simply something consisting of freely-flowing particles. Franklin also understood the concepts of “opposites attract” and “likes repel,” because he noted that objects with a deficit of electric fluid were attracted to objects with an excess of electric fluid, and that two objects in the same state – if both had a deficit or both had an excess – repelled one another. This fluid could also flow from areas of excess to areas of deficit. His “fluid,” as we now realize, actually describes individual electric charges we called electrons and protons [5]. One of the earliest controversies associated with modern electricity came as a result of Luigi Galvani’s experiments with frog muscles in the late 1700’s. After observing muscular twitches after he accidentally touched his scalpel to a frog’s leg muscle, he began experimenting with different metals to see if he could reproduce the same twitch [6]. He found that if a bimetallic arc (essentially a circuit with two metals connected to one another and the frog muscle or nerve, Figure 1) was made, no source of electricity was necessary to make the leg twitch. Galvani reasoned that since there was no outside source of electricity, the source was “animal electricity” in the leg itself, claiming it to be the life force of all animals. However, about a decade later, Alessandro Volta emerged with a new interpretation: his theory stated that the twitch was caused by contact between the two different conducting metals Galvani had been using. In order to prove that it was the different metals and not the frog leg causing the movement, Volta removed the frog from the experiment and enhanced Galvani’s design, creating the earliest voltaic cell. It consisted of a piece of cardboard soaked in salt water, with pieces of copper and zinc placed within it: this caused a chemical transfer of charges between the metals, inducing a current or electron flow [7]. The unit “Volt” was named after Volta and it represents the electric potential between two points. From this new electric source, Michael Faraday was inspired to develop the electric generator, which employed a changing magnetic field to produce a current. This was the first instance of using mechanical energy to create electricity, a fundamental element of future dams. This generator was used to provide electricity to the household.

Evolution of Household Electricity Thomas Edison was the first person to harness current electricity in a way that would provide this energy at an affordable price to households. It began with his search for a more efficient light bulb because in his time, light bulbs burned out after only a few minutes. Edison created a light bulb whose filament was in a small vacuum, a space essentially empty of matter, so that the filament itself would not be forced to burn out by other materials in the air around it [8]. After inventing the light bulb, Edison engineered the first electric station, the Pearl St. Plant in New York City, to supply the electricity for his bulbs. He provided electricity through direct current (DC), which means that the voltage did not come in cycles but instead directly as 110 volts, using large dynamo generators. However, the problem with DC current was that it could not be transmitted over long distances. The resistance of the wire produces a voltage drop whose magnitude increases with the length of the wire. This issue was resolved when Nikolas Tesla patented a system for creating alternating current, which produced voltage in cycles (AC) in 1887 [9]. George Westinghouse, a company owner, saw Tesla’s invention as the future of long-distance transmission, so he bought Tesla’s patents and hired Tesla after Edison rejected him. This lead to a rather vicious “War of the Currents,” during which Edison killed dogs with alternating current to prove that it was more dangerous than direct current. The war eventually ended with Tesla and Westinghouse as the victors when Tesla used turbines to harness the mechanical power of Niagara Falls into alternating current and provided electricity to cities hundreds of miles away. In the United States, the Westinghouse Company chose to standardize the operating frequency to 60 Hz, as suggested by Tesla, eliminating nine other possibilities. In Germany, however, the standardization was much simpler because one company, BEW, had a monopoly on electricity. The outcome of BEW’s standardization was 50 Hz, which was most likely chosen because it fit better with the 1, 2, 5 metric standard. This same company chose to supply its consumers with more power by raising their voltage from 110 volts to 220 volts in 1899. This trend, as well as the 50 Hz operating frequency, spread across Europe over the next few decades [10]. It has been suggested that the US switch to the 220-volt system. In the 1950’s the US did consider switching but then decided against it since most consumers already had a number of 120-volt products. A compromise was reached when the US employed Edison’s three-wire system: one wire supplied +120 volts, another supplied 0 volts, and a third supplied -120 volts, so that stoves, washers and dryers, and other large appliances could access 220 volts, while smaller appliances could still operate on the lower 120 volts [10].

The Electric Plug Edison’s plants provided light to Wall Street, New York City, and London [11]. Edison had thought of a number of applications for this power, including a system for household wiring that used the existing piping of the house as its framework [12]. However, there was no convenient way of tapping into this power for anything other than lighting. Amateur inventors came up with a number of appliances that had to be directly wired to the household system, including Harvey Hubbell, who designed a “Separable Attachment Plug” that connected directly into a light socket. This plug had to be wired to the appliance, but the user would not have to deal with live wires connected to the house. He then improved upon his own design by making the plug itself able to separate: one portion of the plug could be left in the socket, while the other was a two-prong plug that could be separated from the socket plug [13]. After Hubbell’s innovative plug, the next advancement came from a man named Philip F. Labre in 1928 [14]. In order to reduce electrical shock as a result of a short circuit (an undesirable connection), he added a third ground prong to the plug to be inserted into a third hole in the socket. When a person unknowingly creates a short in a circuit with an electrical plug, his body becomes the only path from the live wire of the plug to the ground. Labre added the third prong as an alternative “path of least resistance” to bypass the person. This means that instead of flowing through you, the electrons flow through the ground prong to the earth. [4]. Labre’s outlet is the model for the modern outlet. Aside from the ground prong, there are two prongs that connect to the live and neutral wires. The live wire carries current into the appliance, while the neutral wire carries current back to the electric panel, completing the circuit [4:3]. Without the grounding, Labre’s outlet would be called “unpolarized” because the two identical prongs of the plug may be inserted into the outlet in one of two ways [14]. A “polarized” outlet allows the plug to be oriented in only one way (“Household Wiring”). Worldwide, some plugs have different-sized prongs (like in the US), some are set at different angles (like in some European countries), and some can have completely different shapes (like in Japan). Hustvedt/Wikimedia Commons Another safety advancement in electrical outlets is the Ground Fault Circuit Interrupter. These are the outlets in your bathroom that have the two buttons for ‘reset’ and ‘test.’ Normally, a circuit breaker will flip at about 20 Amperes of current, stopping its flow. The GFCI detects the current flowing through the circuit, and if there is slightly less returning than being sent out (on a scale of milliamperes), it will flip off the power to that circuit [15]. This type of outlet can prevent accidents like fatal shocks from hair dryers falling in bathtubs to smaller shocks from touching the casing of a faulty electrified appliance. Some appliances now come with their own GFCI plugs. Aside from these necessary safety innovations, a number of other innovations have come from the simple electrical outlet. Kim Gerard came up with the idea of a rotating outlet to ensure that bulky plugs can fit together (Fig. 2). The outlet looks like a normal electrical outlet except that inside, the socket is attached to a copper ring that makes electrical contacts with an outer copper ring attached to the outlet casing to ensure that electricity is supplied to the appliance even during rotation [16]. Kiddo/Wikipedia Another extremely convenient invention was the electrical adapter for use abroad (see Fig. 3). Upon observation, it is clear that the adapter does nothing more than provide the correct shape plug for the socket. There is a plastic casing that surrounds two metal contacts. The original plug that connects to these contacts is directly connected to the protruding prongs of the adapter. Unfortunately, there have been no agreed upon international standards for the shape of an electrical outlet or its operating voltage and frequency, so, when traveling abroad, you must use a transformer and/or a voltage converter. These devices use a circuit, and usually a coil, to increase or decrease the output voltage of the electrical outlet you are using based on what you need. American appliances usually require lower voltages than European appliances. This stemmed from the choice by BEW to switch their plants to 220 volts, which eventually spread to Europe, while America chose to remain at 110 +/- 10 volts.

Future of the Electrical Outlet With so little change to the outlet in the past few decades, what could we possibly expect to change in this simple piece of engineering? Well, in the near future, an outlet may provide broadband Internet, a service some companies are testing to determine its practicality. While some electric companies do not want to deal with providing broadband in addition to electricity, it may be useful to rural communities who currently receive only electricity [10]. One of the problems with the power-line Internet is the path it follows, down the line and through the transformer. A transformer decreases the voltage of the incoming power in order to put it at safe levels for the household. When the broadband data travels through the transformer, some of it is lost. In response, the Current technologies and Cinergy Corp. created a coupler to allow the data to bypass the transformer [18]. Internet through the outlet may not be as far out as it seems. Conclusion Where would we be today without Edison’s light bulb, Tesla’s coil, or Hubbell’s Separable Attachment Plug? Chances are we would be sitting by gaslight, using steam-powered generators to power our extremely slow “computers.” The electrical outlet has been a modern convenience for over a century, and while it seems so simple, it has gone through a long, complex evolution. Although it has been set in its ways for several decades, the electrical outlet still seems to have a prosperous future, not only in electricity, but communications technology as well.