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"I'm not a hero, I'm just a physics nerd."—Dave, The Sorcerer's Apprentice
I've had The Sorcerer's Apprentice on my list to review since the first time I saw the trailer. Dave (Jay Baruchel) is a senior physics major working on Tesla coil experiments at New York University. He pines for Becky (Teresa Palmer), a Physics 101 student and late-night DJ for the campus radio station. Early in the film, Dave encounters Balthazar Blake (Nicolas Cage), who reveals Dave is Merlin's heir and the "Prime Merlinian" destined to battle the evil witch Morgana. Balthazar imprisoned Morgana in the "Grimwald" hundreds of years earlier, but an evil sorcerer, Horvath (played by Alfred Molina), wants to free her.
Before Dave can take on the bad guys, he needs to learn some magic from Balthazar, including levitating, conjuring fire, and shooting "plasma bolts" from his hands. Along the way, Dave demonstrates his science knowledge, and several scenes could be used in a physical science or physics class.
Many of the film's most spectacular effects involve Dave's Tesla coils. (Overlooking the dubious premise of an undergraduate having access to hundreds of thousands of dollars worth of equipment and unsupervised access to a huge lab space, the setup is pretty cool.) The Tesla coil is named for Nikola Tesla, a 19th-century scientist famous for his electrical experiments. Tesla worked primarily with alternating current (AC), while Thomas Edison worked with direct current (DC). A great debate occurred about which kind of electricity should be used to illuminate U.S. homes. Both scientists performed public demonstrations to show the superiority of their systems, but in the end, Tesla won. Worldwide, household electricity is delivered as AC (the voltage alternates from positive to negative 60 times per second, and the current changes direction with every cycle). Batteries, which are DC, provide a constant current.
Nicolas Cage as Balthazar Blake in The Sorcerer's Apprentice.
A Tesla coil is an AC device capable of generating extremely high voltage with relatively large current, and therefore arcs, or long electrical sparks. (See this Wikipedia article for more details.) One way to comprehend voltage and current is to think about a waterfall. Its height is analogous to the voltage difference, while the size of the river is like current. Just as a water droplet falling from a great height isn't very dangerous, a static shock from dragging feet across a carpet won't really hurt you. On the other hand, a large volume of water can knock you down, even if it is only falling over a small drop. Similarly, a car battery maintains only a 12-volt difference between the poles, but can produce enough current to be deadly. A Tesla coil can produce voltage differences in the 10,000–100,000 range, with currents large enough to be lethal.
In The Sorcerer's Apprentice, Dave sets up his Tesla coil to play a tune for Becky. I initially thought that was taking the science a step beyond the practical. It turns out, however, that the practice is actually old news: You can find videos of "singing Tesla coils" on YouTube. The frequency of the Tesla coil discharge can be manipulated, changing the pitch heard as the sparks fly. The tones will never be pretty; they sound a lot like early video game sound effects.
When Dave shows his Tesla coil to Becky, they stand inside a chain-link box about the size and shape of a phone booth. This sort of electrically conductive box is called a "Faraday cage," and it is used to protect people and sensitive electronics from discharges around a Tesla coil. Electrical current stays on the outside of any conductor, and the electric field inside a metallic shell is zero. This explains why being inside a car keeps you relatively safe during an electrical storm. If the car is struck by lightning, the current will stay on the outside and not enter the car's interior. Check out this somewhat silly video of an English TV presenter trying this on Top Gear.
When Dave asks his new mentor how magic is possible, Balthazar replies with the tired line that normal people only use 10% of their brain, but sorcerers also use the other 90%. The idea that normal people don't use all of their brain is a longstanding truism that actually is false. While at any given moment, only a small percentage of synapses may be firing, CT scans show activity is happening throughout the brain. Snopes.com offers a good debunking of this misconception.
Sorcerers also are apparently able to use the electrical energy of their nervous system linked to the Earth to get energy. This explains why Dave has to exchange his rubber-soled shoes for a pair of leather-soled "old man shoes," as he calls them. While rubber is a much better insulator than leather, neither is a conductor. The small current a person produces might flow through leather soles, but only if they were very wet.
I have written before about how scientists are portrayed in films, noting the “mad scientist" is a popular stock character, even though in reality, they are extremely rare. Dave is a fairly typical representation of a physics major: He is physically weak, has difficulty in social situations, and dresses poorly; his voice often takes on a rather nasal tone. But he is "adorkable": He is genuinely nice to Becky, and he strives to become more outgoing through the course of the movie. In the end, his battle with Morgana resembles the troubling stereotypical conflict of masculine science versus feminine "witchcraft." Just once, I'd like to see a female science nerd save the world by defeating a powerful warlock.
The Sorcerer's Apprentice contains plenty of opportunities to generate excitement about electricity in your high school physical science or physics class, while biology teachers might discuss the misconceptions about how much of his or her brain the average person uses.
Jacob Clark Blickenstaff is Assistant Professor of Physics and Assistant Director of the Center for Science and Mathematics Education at the University of Southern Mississippi. He can be reached at firstname.lastname@example.org.
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