The first documentation of static electricity dates back to 600 BCE. Even after 2,600 years’ worth of tiny shocks, however, researchers couldn’t fully explain how rubbing two objects together causes it. But according to a team at Northwestern University, the mystery is finally solved. As explained in a September 17 study published in the journal Nano Letters, the answer is “surprisingly simple.” It all has to do with little imperfections.
“People have tried, but they could not explain experimental results without making assumptions that were not justified or justifiable,” Lawrence Marks, a professor emeritus of materials science and engineering, said on September 18. “We now can… Just having different deformations—and therefore different charges—at the front and back of something sliding leads to current.”
Marks and their colleagues first began exploring static electricity’s properties back in 2019, when they discovered that rubbing two materials against one another bends miniscule variations on each object’s surface. This movement then generated voltages. From there, the team created a new model that relies on the concept known as “elastic shear,” which happens whenever an object resists a sliding force and creates friction in the process. Once the friction builds up on either side of the nanosized deformations, the difference in electrical charges can create a current—and the resultant shock.
“We developed a new model that calculates electrical current. The values for the current for a range of different cases were in good agreement with experimental results,” said Marks.
Marks notes that while most people associate static electricity with demonstrations such as hair-raising elementary science experiments or touching a doorknob after rubbing your pet’s fur, the electric charge actually exerts a huge influence on the world “in both simple and profound ways.” An everyday example can be seen when a coffee grinder’s charged grains alters the flavor of beans. But static shocks are also responsible for far more serious issues, such as dosing complications for powdered medicines and industrial fires. Most experts believe the Hindenburg tragedy likely hinged on fires sparked by static electricity. By better understanding the mechanisms involved, experts across industries can help make their products more effective and working conditions safer.
[Related: Butterflies and moths suck up pollen with static electricity.]
“The Earth would probably not be a planet without a key step in the clumping of particles that form planets, which occurs because of the static electricity generated by colliding grains,” Marks explained. “It’s amazing how much of our lives are touched by static electricity and how much of the universe depends on it.” And now, after thousands of years, that key phenomenon has an exact explanation.