The first description of static electricity dates back to 600 BC. e. and was made by the Greek philosopher Thales of Miletus. This seems incredible, but scientists only recently understood the physics of the phenomenon, having completed a series of studies in the field of the occurrence of static charge. This discovery could have critical implications for many areas, from industrial safety to power generation for wearable and connected electronics.
Image source: Pixabay
Cats have proven to be particularly good at generating static electricity. Firstly, you want to stroke them, which, in fact, could have stopped there. Secondly, and mainly, it all started with the fur that was used to rub amber, as mentioned by the inquisitive Greek. Therefore, although cats are not the main culprits of static electricity, their fur is an ideal conductor, and the discharge most often strikes their owners and sympathizers.
Scientists from Northwestern University in the suburbs of Chicago have put an end to the study of the secret of the occurrence of static electricity. They completed a series of studies of this phenomenon that began in 2019, collecting all the necessary data to describe the physics of the process. Four years ago, scientists realized that nanoscale deformations of the surface of rubbing objects and the sliding process play a key role in the occurrence of a static charge.
The latest research in 2024 explored how nanoscale deformation and sliding lead to the distribution and accumulation of charge, which results in a noticeable “electric shock” when, for example, we pet a cat. The lower the air humidity, the higher the likelihood of a discharge. Scientists recommend wiping your cat’s fur with a damp cloth first to avoid static discharge if you’re concerned.
«For the first time, we can explain a mystery that no one could solve before: why friction matters,” explained lead author Laurence Marks, a professor of materials science and engineering at the university. — People tried, but could not explain the results of experiments, making unfounded assumptions. Now we can justify it, and the answer is surprisingly simple. Different deformations in front and behind the sliding object lead to the generation of current.”
To confirm the experimental results, the researchers created a model that estimated the electrical currents caused by friction. They called this phenomenon “elastic shear.” Essentially, charge is related to the applied force and friction – as described by Newton’s third law (action equals reaction) – and how charges are displaced during the sliding process. When materials with nanoscale deformations rub against each other, they create a static charge potential difference between the leading and trailing edges of the objects, leading to charge accumulation and eventual discharge.
Image source: Nano Letters, 2024
«Static electricity affects life in both simple and profound ways, Marks said. — Charging the beans with static electricity has a big impact on the grinding of the coffee beans and their taste. Earth likely wouldn’t be a planet without the key step of clumping together particles to form planets, which occurs due to static electricity generated by colliding granules. It’s amazing how much of our lives and the universe depends on static electricity.”
On a practical level, there are several ways to minimize static shock, such as choosing clothing made from natural fibers, walking barefoot, and increasing indoor humidity. Humidity below 40% enhances the conductivity of the “elastic shear” process. If your cat shocks you, especially in winter, you can neutralize the charge by petting it with a damp cloth. However, it may be better to shock yourself rather than shock your pet if he doesn’t like the wet washcloth. Cat hair, unfortunately for owners, is an excellent source of electrostatic charge.
«The polarization and associated charges in front and behind the rubbing objects are not the same, and the difference between them leads to the flow of current, similar to how the difference in air pressure above and below the wing of an airplane creates lift,” the researchers explained in a paper recently published in the journal Nano Letters.