In this blog post, we’ll explore the principles behind the static electricity we commonly experience, as well as situations where it can lead to unexpected accidents in industrial settings or daily life.
Every reader of this post has likely experienced that tingling sensation from static electricity. Static electricity strikes unexpectedly—when you touch a doorknob in winter, when putting on or taking off a thick sweater, or even when shaking hands. If you have naturally dry skin, you may have looked up ways to prevent static shocks because of frequent tingling sensations. But have you ever imagined that this static electricity—which is usually just a bit painful and annoying—could lead you into an emergency situation? In fact, the impact of static electricity runs much deeper in our daily lives than we might think. Beyond mere inconvenience, static electricity can lead to fatal accidents in industrial settings or medical environments. Let’s take a closer look at the nature of static electricity and its dangers.
Before exploring static electricity, we need to first understand what electricity is. Every object in the world we live in is composed of atoms, the basic building blocks of matter. An atom consists of a heavy nucleus carrying a positive (+) charge and light electrons carrying a negative (-) charge. Compared to the heavy nucleus, electrons are light and can move freely from one object to another. Because of this, the amount of negative charge in an object can become greater or lesser than the amount of positive charge. This imbalance in charge generates an electrical force, which we use to power machines, transmit information, and even regulate the nervous systems of living organisms. An entire object can also carry a positive or negative charge. Furthermore, positive and negative charges possess a force that attracts each other, much like the north and south poles of a magnet, and this force serves as the source of electrical energy. Electricity refers to the charge and electrical energy generated by electrons in this way.
Static electricity means “electricity at rest.” When an object or its surface has a greater abundance of either positive or negative charge, we say it is charged; static electricity refers to an object remaining in this charged state without movement. The most common form of static electricity we encounter in daily life is that generated by friction. Every object has a relative tendency to gain or lose electrons, so when two different objects rub against each other, electrons move from one to the other. If you go to a mirror right now and comb your hair with a comb, you will see that hair sticks to the comb. This may seem like a simple phenomenon, but the energy generated by the movement of electrons during this process can be utilized in various ways. For example, one application of static electricity is the electrostatic printer, which can print text and images using the principle of static electricity without ink. As the hair and comb rub against each other, the side that loses electrons becomes positively charged (+), and the side that gains electrons becomes negatively charged (-), and they stick together due to the attractive force between positive and negative charges.
So, what does it mean when we say “I got a static shock” or “Static electricity occurred!” when we feel a tingling sensation after touching a doorknob? The precise description of this tingling sensation is a spark discharge caused by static electricity. When a charged object comes into contact with another object, the charge escapes; this is called a discharge. When the discharge occurs over a small area, such as when your fingertip touches a doorknob, electrical energy is released during the discharge process, causing sparks to fly—resulting in a spark discharge.
Our bodies become charged through friction between our skin and the clothes we wear, and when we grasp a doorknob in this state, this static electricity spark discharge occurs. Interestingly, such discharges can lead to much more serious problems in extreme environments. For example, even a small static discharge in a data center packed with electronic equipment can damage sensitive devices, causing massive economic losses. This buildup of static electricity occurs more frequently in winter, particularly because water molecules in the air are electrically conductive and help discharge charged objects. In the dry winter air, there are few water molecules, so our charged bodies cannot be properly discharged, leading to more instances of touching doorknobs while still electrically charged.
But could this stinging static spark discharge really kill us? Fortunately, the answer is no. It is known that when we touch a doorknob or take off a sweater, a voltage exceeding 10,000 V (volts) and a current of about 15 mA (milliamps) are generated momentarily. Simply put, voltage represents the amount of energy possessed by each individual electron, while current represents the number of electrons flowing per unit of time. The number 10,000 might seem alarming. However, the actual harm to the human body depends on the magnitude of the current and the duration of the current flow. Therefore, a static discharge involving a small current of about 15 mA flowing for a very short time causes nothing more than a slight tingling or prickling sensation. However, in some industrial settings, small sparks caused by static electricity can ignite flammable gases or dust, potentially causing an explosion. If the resulting spark spreads to flammable materials, it could lead to an explosion or fire.
In fact, the truly dangerous form of static electricity is lightning. Clouds are sometimes charged with an amount of electricity that is incomparable to that of the human body. Lightning is the phenomenon where this immense charge in the clouds discharges through the air, and when it discharges into an object on the ground, it is called a lightning strike. If that object on the ground happens to be you, it can be quite dangerous because a very large current flows through your body—unlike when you simply touch a doorknob. However, the probability of being struck by lightning is very low, so there is no need to fear it. Instead, it is more important to understand exactly how lightning rods installed on buildings to prevent lightning strikes work, and to ensure safety through this knowledge. However, even in the case of a lightning strike, the duration of the current flow is very brief, so the chances of surviving a lightning strike are actually quite high.
So far, we have clarified the exact meaning of the term “static electricity,” which we commonly use in daily life, and explored several static electricity phenomena. The title, suggesting that one could unintentionally die from static electricity, may have caused some confusion among readers. Although static electricity is a common phenomenon in daily life, failing to understand it properly can expose you to unexpected dangers. If we all know and use the precise definitions of these terms, we will be able to avoid such pitfalls in the future.
