Northwestern University scientists have made a new contribution to understanding a long-standing phenomenon called static electricity.
In their most recent research, the researchers found that such mundane activities as petting a cat or rubbing a balloon across your hair can generate static charge due to the minute deformations on an object's surface.
Science of Static Electricity
Thales of Miletus was a famous philosopher from ancient Greece who discovered that dust is attracted easily when you rub amber with fur. Gizmodo reports that this triggers static electricity.
Today, we know what static electricity is, created through different acts. This is ironic since some animals, like ticks, use the electrical charge for better adhesion to their hosts. However, science has struggled with the question of what happens when rubbed surfaces create static electricity.
"For the first time, we can explain a mystery that nobody could before: why rubbing matters," Professor Emeritus of Materials Science and Engineering at Northwestern Laurence Marks said.
"People have tried, but they could not explain experimental results without making assumptions that were not justified or justifiable. We now can, and the answer is surprisingly simple," he added.
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The Balloon Trick: The Classic Example
Most of us have played the classic balloon trick. Rub a balloon on your head to give yourself static electricity, causing your hair to stand upright. This is because the friction between two objects - in this case, rubbing one's head against a balloon- is different physically, which causes the electrons to be transferred.
In this experiment, the balloon gathers the electrons, yielding a negative charge, while the hair loses electrons to create a positive charge. On coming into contact, these two objects attract each other through different charges, allowing the electrons to flow rapidly between them. This principle also explains why stepping on a carpeted floor, touching a metal doorknob, and many similar combinations can cause a mild shock.
New Discoveries
Previous work had suggested that rubbing similar materials produced static electricity, but what caused this phenomenon remained unknown.
Lead researcher Marks and his colleagues finally made history by developing a new mechanism that could explain static charge generation from rubbing and published their renowned work in Nano Letters.
Earlier, they had already discovered that rubbing surfaces against each other resulted in minute deformations that led to voltage development. Their latest findings indicate that the elastic shear behavior of materials resisting sliding along surfaces—is the key to it all.
Reading Elastic Shear and Friction
According to the authors, friction buildups from elastic shear create opposite deformations on either side of an object, enabling it to stack charges against each other.
It's rather like how air pressure differences cause lift for airplanes. The group said they developed a new model that measures electrical current, aligning with their experimental findings.
Marks said they had the seed of what was happening in 2019. He added that it needed time to grow, just like all seeds.
Related Article: Researchers Discover Static Electricity Attracts Ticks to Latch on People, Pets
