DC vs. AC Whodunit: Murdoch Mysteries "Power"

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Since I don't watch TV, I was unaware of a Canadian police detective series titled "Murdoch Mysteries," which is cast in Toronto at the turn of the 20th century. Melanie found a DVD at the library with season 1 episodes, and noted that the first show was "Power," with a storyline based on the debate over whether Thomas Edison's DC current was safer than Nikola Tesla's AC current (Tesla was backed by George Westinghouse). You might be familiar with the heated and often violent exchanges that really happened between the two camps, often referred to as "The War of Currents." After all, a lot of money, status, and control depended on the outcome. We know now that AC eventually won the battle. My interest in watching "Power" was mostly to look for inconsistencies and outright errors in the technical aspects of the show. Movie producers are notorious for asserting way too much creative and artistic license when portraying science concepts - often to the frustration of qualified consultants who recommend otherwise.

As in real life, animals as large as elephants (YouTube) were routinely electrocuted to death in public demonstrations to convince the public DC was safer than AC. The TV show's plot planned to subject a Golden Retriever to 1,000 volts of evil AC, but the stunt takes a dark turn when the town's beauty queen becomes the victim instead. Detective William Murdoch's job was to determine the cause of death and sift through the lineup of likely suspects. Just as Sherlock Holmes had the help of Dr. John Watson, Murdoch has Dr. Julia Ogden to discover the medical aspects of a crime.

Arguments for DC current were centered around the relatively low distribution voltage levels, versus the kilovolt levels of AC distribution. To some extent the reasoning is valid insofar as since other than compensation for line voltage drops, distribution voltages did not exceed that which the end user would see. That is, there were no kilovolt DC distribution lines because unlike with AC, there was not (and still is not) a simple and efficient means of transforming DC voltages to higher or lower values at a distribution system scale. Ironically, what made DC 'safer' than AC is what made AC more efficient to distribute than DC. DC power systems require many local generating stations whereas AC systems can have large generation facilities and a network of transformer substations located at great distances. Efficiencies of scale naturally make AC distribution the superior choice.

Why is high voltage better, you might ask if you are not familiar with distribution systems? The simple answer is that power losses in the conductors are proportional to the square of the current flowing through them. Per Ohm's law, P = I²•R, where R is the resistance of the transmission line. Since R is fixed by the metallic composition, cross-sectional diameter of the wire, the way to transfer power with the lowest line loss is to keep the current (I) as low as possible. Since P = I•E, for a constant value of P, E (voltage) must increase in inverse proportion to I. Cranking the voltage up by a factor of, say, 1000, means the current decreases by 1/1000 to get the same amount of power. That results in only one millionth (1/1000²) of the power being dissipated in the transmission line, thereby vastly increasing the system efficiency. Sure, you could generate kilovolt DC currents for distribution, but stepping it down to usable levels requires either wasting significant power dissipating it through a voltage divider, or building DC-DC converters. Transformers are much simpler and more reliable (fewer failure-prone components).

Overall, I give "Power" a thumbs up for not stretching the limits of credibility too far. All the 'regulars' in the casting are likeable IMHO, which is no trivial claim for me to make of any TV show. Nicola Tesla appears in the episode as the reserved, quiet genius he was in real life, and assists Detective Murdoch with his investigation. There were a few scenes where his concepts of wireless power transmission and wireless voice communications were depicted. Detective Murdoch, it turns out, is a science aficionado who has a good grasp of physics principles and refers to Tesla as one of his heroes. Had Sherlock Holmes known Nikola Tesla, they, too, would have been mutual consorts on such matters.

I won't spoil the show by divulging the perpetrator - or perhaps perpetrators - of the crime. The "Power" episode can be viewed on Amazon and other websites. I could not locate a free venue for it.

BTW, I found a website called "The Science of Murdoch Mysteries " that does a good job of investigating Detective Murdoch's investigations for technical accuracy and viability. There is another episode with Tesla (which I have not seen), called, "The Tesla Effect."

Posted July 28, 2016