This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: If you mount a pickle on two metal forks and plug it into a socket, one end will light up in a brilliant orange glow. It's a classic K–12 science demonstration, but the exact physics behind the illumination has long remained a mystery.
Josh Méndez, an assistant professor of electrical engineering at Portland State University, was surprised to learn that the glowing pickle was still an unsolved electrostatics problem. As a scientist with an interest in obscure electrostatic problems, Méndez felt called to delve into the pickle jar. More than 100 burned pickles later, he is finally approaching an answer.
Because pickles are soaked in salty brine, they readily conduct electricity. When a current passes through, two competing theories usually explain the resulting glow: a spark discharge or the ignition of hydrogen gas. The first theory relies on vapor sparks.
As current heats the pickle, it boils off liquid, leaving behind gas pockets and a pungent smell of burned pickle mixed with hot metal. However, the gas pockets also stop the flow of electrical current, causing the pickle to cool down. When this happens, the gas pockets shrink and the conductive brine comes back toward the electrode.
"As that water comes back in toward the electrode, a little arc crosses between the liquid and the electrode, just as when you reach for a doorknob and you get a zap," Méndez said. "That doesn't explain everything that happens, though." For instance, it doesn't clarify why only one end glows. The second theory points to chemical ignition via electrolysis, which splits the brine's water into oxygen and volatile hydrogen ions.
Hydrogen is only produced at the negative electrode, which may explain why the pickle glows on only one side. In this scenario, the glow comes from tiny hydrogen explosions caused by the intense heat from the electrodes and trapped inside the pickle. Méndez's research indicates the real cause is a hybrid of both theories: The electrical spark actively ignites the hydrogen gas.
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