The Current War is a movie that discusses the competition on the electricity market between Thomas Edison, George Westinghouse, and Nikola Tesla, which determined whose electrical system would power the modern world. Edison has decided on Direct Current (DC), but it is limited in range and expensive. Westinghouse sets out to prove Alternating Current (AC) can work over longer distances at a significantly lower cost. Edison and Westinghouse compete to get cities across the United States to use their system. Edison suggests that AC is dangerous and engages in a publicity war, while Westinghouse stands behind the technical merits of AC. As Edison struggles to find ways to make DC more affordable, Westinghouse attempts to get the high voltage AC system to work with motors.
So what is the difference between these two systems? In the YouTube channel, AddOhms, explains that in DC, the current flows through one direction and follows the exact rotation to complete its route. In this current, the voltage stays constant through time. If the battery has limited energy, the voltage level will begin to decline as the time passes. Below on the left, we see the example for DC and on the right for AC. In the AC, on the other hand, current also flows in one direction as the voltage reaches to peak and goes back to zero. At the zero levels, the polarity changes, causing current to flow in the opposite direction which completes the cycle. The cycles are measured using the unit Hertz that means cycles per second. It can either be 50 Hertz or 60 Hertz depending on the region. It means that the cycle repeats itself at least 50 times. Therefore, our light bulbs are actually getting on and off 50 times per second, but since our vision capacity cannot capture that, we see the light constantly.
In the movie, Edison’s DC competes against Westinghouse and Tesla’s AC to dominate the American electricity market. We see the politics behind the competition and how it made a difference in our lives. One of the examples is that Edison invents the machine to show how AC kills and uses it on a horse. Later, his idea becomes the main pillar of the electric chair used in prisons. If you are interested in the background story of the light enlightens your room, you can go to this movie.