Scientists at Northwestern University may have figured out why walking on the carpet in socks, petting a furry friend or rubbing a balloon in your hair creates static electricity. In a new study, they found that friction can produce tiny deformations on the surface of an object, causing this phenomenon to occur.
People have known about the existence of static electricity for thousands of years, and the earliest recorded observation of static electricity is thought to be by Thales of Miles, a Greek philosopher in 600 BC (Thales noticed that fur rubbed with amber Instantly absorbs dust). Since then, we’ve learned that many things generate static electricity, which is beneficial to animals, such as ticks using static electricity to extend the grapple range of their hosts. But scientists still don’t know many of the basics behind static electricity, especially why friction often induces static electricity – at least until now.
“For the first time, we can explain a mystery that no one has been able to explain before: why friction matters,” lead researcher Lawrence Marks, professor emeritus of materials science and engineering at Northwestern University, said in the university’s statement. “People have tried, But they couldn’t explain the experimental results without making unreasonable or unreasonable assumptions. Now we can, and the answer is surprisingly simple.
Most people have seen the classic balloon trick, where rubbing a balloon on your head creates static electricity that makes your hair stand on end. The basic principle behind this trick is that rubbing two objects with very different physical properties causes one object (in this case, our hair) to lose electrons and become positively charged, while the other object becomes negatively charged (gain electrons). When the objects meet again, the charge difference causes them to attract each other and cause electrons to move quickly from one object to the other. The rapid movement of electrons also explains why rubbing our feet along carpet and then touching a metal door handle causes a slight vibration. But rubbing pieces of the same material can also create a static charge, and previous research seems to have debunked a common explanation for why this happens (the argument is that such a charge can be created by rubbing two different-sized pieces of the same material).
In the new study, published last month in the journal nanolettersMarks and his team say they have discovered another major mechanism to explain why friction causes static electricity. In 2019, they published a study that found that the mere act of rubbing two materials together caused tiny deformations in the object’s surface, which produced a voltage. But they have now figured out exactly how friction causes electrostatic charging, which is affected by elastic shear, or the material’s ability to resist sliding as it moves along a surface (which is why we end up with stops sliding on the floor) when wearing socks ). They believe that the increased friction caused by elastic shear means that the front and back sides of an object may deform differently, carrying opposite charges, causing static electricity, similar to how the difference in air pressure above and below an airplane wing causes lift. .
“In 2019, we planted the seeds of what was to come. However, like all seeds, it takes time to grow,” Marks said. “Now, it has blossomed. We have developed a new model for calculating the current. The current values for a series of different situations are in good agreement with the experimental results.
Other researchers will have to verify the results, and while this hypothesis may help explain many types of static electricity, including that produced by rubbing the same materials together, it cannot explain everything. Still, it’s strange that science has a lot of mundane mysteries to solve when trying to understand the world around us, which means there’s always something new to learn.
