Citizen Science #22 by Jamie Zvirzdin

Energy Demystified: The Bolts and Volts of Electric Energy

“With an anxiety that almost amounted to agony, I collected the instruments of life around me, that I might infuse a spark of being into the lifeless thing that lay at my feet,” Dr. Victor Frankenstein says in Mary Shelley’s “Frankenstein,” On this dramatic night, set not in a Gothic castle in October but in a German city apartment in November, he would harness the raw power of electric energy.
Even though Mary Shelley mentions galvanism in Chapter 2 of the novel—alluding to Luigi Galvani’s early experiments “animating” dead frogs with channeled lightning, making frog muscles convulse—Shelley never explicitly wrote that Victor placed bolt-like electrodes on the monster’s neck, nor that Victor used electricity to animate his Creature. All the same, subsequent movies—particularly James Whale’s 1931 film adaptation—and our collective imagination over time have solidified in our minds the spooky castle, the laboratory with wires and glass tubes, lightning and thunder, bolts and volts.

Perhaps this is because electricity still seems as mysterious as life itself, even entwined with life itself: our brain cells send pulses of electricity to talk to each other, and shock paddles (or sticky defibrillator pads, more frequently used since COVID-19 began) can restart failing rhythms of the heart. And we all know you should never climb over electric fences—particularly ones from Jurassic Park. So what exactly is this enigmatic power that can, indeed, spark life—or destruction?
At its core, electric energy is the work done to move electric charges. If, like Sisyphus, I push a boulder uphill, it takes effort—and that effort is stored as gravitational potential energy (for more about potential energy, read Citizen Science #16, “Potential Energy’s Untapped Value,” on Allotsego.com). Likewise, when we move electric charges against an electric field, we store electric potential energy. The energy stored is proportional to the amount of charge moved and the strength of the electric field. This energy can then be released, performing work—lighting a bulb, heating a filament, or, in Dr. Frankenstein’s case, animating something far more extraordinary.

Consider a thunderstorm, nature’s best display of electric energy. Through complicated collisions and Sisyphean updrafts within the storm, particles with negative charges are driven toward the cloud base, with positive charges accumulating near the top. This separation creates a large electric potential difference (voltage) between the cloud base and the ground below, because the ground often becomes positively charged in response.

This potential energy remains stored as long as air (a poor conductor) separates the charges. But once the potential difference becomes strong enough to overcome the insulating properties of air, negative charges, invisible to our eyes, begin to snake down the sky. When one of these “leaders” nears the ground, positively charged particles on the surface surge upward to meet it—people report that just before lightning strikes, their hair will stand on end, their skin tingles, they’ll have a metallic taste in their mouths, they’ll hear crackling or buzzing metal objects, and other signs—all evidence of positive charges moving upward, attracted by the snaking leaders.

When the charges meet, completing the conductive channel, the electric energy is unleashed and the current travels back up the bolt, illuminating the sky…as well as any hideous beings lurking about in the storm, as Dr. Frankenstein experienced while hiking in the Alps.

“A flash of lightning illuminated the object, and discovered its shape plainly to me,” he says. “Its gigantic stature, and the deformity of its aspect more hideous than belongs to humanity, instantly informed me that it was the wretch, the filthy dæmon, to whom I had given life.” Curiously, in the book, Dr. Frankenstein’s Creature is highly intelligent, articulate, and literate. I’d like to think he’d be curious about the lightning that supposedly created him.

If he asked me how much energy is actually involved in an average lightning bolt, this is what I’d say: Electric energy can be measured in different ways—including through lightning-blasted sand, called fulgarite—but according to the National Weather Service, a typical lightning flash is about 300 million volts and about 30,000 amps. (For comparison, the current in our wall sockets is 120 volts and 15 amps.)

Given a voltage (symbol V) of 300 million volts and a current (symbol I) of 30,000 amps, we start with the formula for power: P = V × I. Substituting these values gives

P = 300,000,000 volts × 30,000 amps = 9 terawatts, or 9,000,000,000,000 watts (W).

This wattage definitely exceeds Hollywood’s estimate from “Back to the Future,” where Doc Brown shouts about needing “1.21 gigawatts!” of power to send a DeLorean through time.

To find the total electric energy, we multiply this power by the duration of the strike. For a typical lightning strike lasting around 50 microseconds (0.00005 seconds), the energy E is

E = 9,000,000,000,000 W × 0.00005 s = 450 megajoules, or 450,000,000 MJ.

This is a fabulous amount of energy. Like Dr. Frankenstein, I do wish we could harness this energy for our own benefit—not to create monsters from dead flesh, perhaps, but to channel it into useful and life-saving devices: lights, cell phones, computers, and medical devices, among many others.

The equation we used for lightning can be modified to calculate our electric energy consumption. My smartphone, for example, has a battery rated at a voltage of 3.85 volts (V) and a storage capacity of 4,680 milliamp-hours (mAh), a unit that combines the current and the time together. We first convert milliamp-hours to amp-hours, giving us 4.68 Ah. If I use the full battery capacity of my phone, the total electric energy I have released from the battery is

E = 3.85 V × 4.68 Ah = 18.02 Wh,

meaning the battery holds about 18 watt-hours of energy (on your electricity bill, you’ll notice that you often pay a certain amount per 1,000 watt-hours, or kilowatt-hours). To convert watt-hours to joules (a more universal unit of energy), we multiply by 3,600 (since 1 watt-hour equals 3,600 joules) to get about 64,800 joules. If I allowed my full phone battery to drain completely until it died, it would use up around 64,800 joules of electric energy. This amount is nothing compared to a lightning bolt—it’s even less than the chemical potential energy in one Snickers bar (250 calories × 4,184 joules/calorie = 1,046,000 joules!). But the more we smartly use electric energy and source it from clean, renewable sources—who knows, maybe lightning itself, someday—the longer we’ll be able to enjoy these marvels without messing around with nature as Dr. Frankenstein did.

“It was already one in the morning,” the well-meaning doctor said that stormy November night. “The rain pattered dismally against the panes, and my candle was nearly burnt out, when, by the glimmer of the half-extinguished light, I saw the dull yellow eye of the creature open.”

As we continue to infuse a spark of being into our dead smartphone batteries, let us remember the power and potential for both creation and destruction as we use bolts and volts to animate our modern-day Creatures.

Jamie Zvirzdin researches cosmic rays with the Telescope Array Project, teaches science writing at Johns Hopkins University and is the author of “Subatomic Writing.”