November 27 2023, 15:01

A very good channel by Kathy Joseph about the history of science, mainly about physics, but with a focus on history.

This video is about how these various voltage standards in household outlets appeared. I just returned from Chicago, and she talks about Chicago’s role in all this. In October 1871, the Great Chicago Fire destroyed much of the city. At that time, Chicago was an important hub on the route to the gold from the eastern coast and was growing rapidly. Houses were built hastily, which is why it all ended so sadly. Ultimately, the city was rebuilt with an emphasis on high-rise buildings. It was around this time that Chicago became the fastest-growing city, not only in population but also upward, in floors. It seems to still hold the record for the highest average building height in the world.

So, besides the problem of making sure houses didn’t fall apart from the wind 🙂, Chicagoans addressed how to prevent them from blowing up due to the gas used almost universally in homes, from stoves to lamps. And lifting gas to the nth floor was also a non-trivial task at the time. In general, the focus on electricity was largely supported by the burgeoning Chicago. The firm “Westinghouse Electric” showcased a column of 15,000 multicolored light bulbs that lit up in a specific sequence; Incidentally, the development of these light bulbs involved the prominent Russian scientist A. N. Lodygin, who was invited to build a light bulb factory. During the exhibition, the Third International Electrotechnical Congress took place, establishing universal international electrotechnical units, named after their inventors: Ampere, Watt, Volt, Joule, Ohm, etc. Regarding Russian scientists: Kathy further talks about Mikhail Dolivo-Dobrovolsky, a Russian-Polish engineer who developed the first three-phase motor in 1891, as well as a three-phase generator and transformer. Their design remained more or less unchanged for at least the next hundred years.

In fact, the high-rise buildings under construction made electricity accessible because less copper was needed per apartment (look up the skin effect). By the way, this was also one of the factors for the “victory” of alternating current, promoted by George Westinghouse and Nikola Tesla, over direct current, promoted by Thomas Edison. And at that moment, different standards spread worldwide. It turned out that direct current simply required more copper for wiring. And significantly more so. Another important factor was the invention of a meter by Oliver Shallenberger, which only worked on alternating current (because it involved a rotating wire, essentially a sort of motor). A vast number of such meters had been manufactured by that time, which also contributed to the expansion.

It turned out that the 110 volt standard was chosen simply because being shocked by such a current had fewer fatal consequences, while still providing sufficient power for various domestic purposes. Thomas Edison tested and soon patented a three-wire electrical network: +110V, -110V, and a neutral conductor.

In the U.S., by the way, not everything is 110V. Looks like today I might go repair a clothes dryer. It’s powered by 220V.

So, returning to the topic. Such a network was sufficient for powering an Edison incandescent light bulb with a carbon filament: it required just 100V, but Edison added another 10%, accounting for potential losses while the current traveled through the wires. In Europe, after 1883, they switched to bulbs with metal filaments, which required voltages exceeding 110 volts. This essentially laid the foundation for different countries, and now it’s prohibitively expensive to change. Look at Japan – they manage to use different frequencies (50 and 60 Hertz) in the same network on the west and east coasts of the country. Some equipment is sensitive to the frequency and requires adapters in Japan (expensive and bulky). But mostly, everything modern still works. Interestingly, in Japan, the voltage is even lower than in the U.S., at 100 volts.