Static electricity develops when there is an imbalance of electric charges on the surface of an object. Most materials are electrically neutral in their natural state, but due to surface interaction with other materials, they gain an electric charge. These charges are referred to as static electricity because they are fixed on the surface of the material and in the area of application until they are later removed by a conductor or an electrical discharge. Many daily human activities cause static electricity, usually little at a time, but when they are able to build up, they can have significant effects.
All materials are made up of atoms that are electrically neutral as they contain equal amounts of negatively charged electrons and positively charged protons. The structure of an atom is such that electrons orbit a positively charged nucleus; therefore, the electrons occupy the outer periphery of the atom. When surface interaction occurs between different materials by rubbing them together, electrons are sometimes transferred between them, leaving one (electron giver) with a positive charge and the other (electron receiver) with a negative charge of equal magnitude. This is known as the triboelectric effect. Some materials such as polyester and rubber are good at receiving electrons, while some others like wool are more likely to lose electrons. There are also materials that do not easily gain an electric charge, such as cotton. Conductors are capable of giving and receiving electrons, but they do not retain their electric charge because when they are charged, all their positive and negative charges are distributed until the electric field is balanced again. Therefore, in order for static electricity to be created, at least one of the interacting objects must be able to hold charges, i.e., an electrical insulator.
Most static electricity effects caused by human activities are based on the triboelectric effect, but the way the electron transfer takes place is still not fully known. The electrons don’t just hop between surfaces as they rub together; they are transferred due to friction. Most times, friction occurs from chemical bonds that rapidly form and break as two surfaces slide past each other. In many chemical bonds, electrons are unequally shared because electrons spend more time on one side of the bond than the other. Those sides are likely to have an extra electron or two when the bond breaks, so they become the electron receivers, and charges are built up that way.
The effects of static electricity on everyday life are mostly unwanted, and sometimes outright harmful. They range from occurrences from clothes clinging to the body to serious fire explosions. When people interact with insulating materials, they often get charged by picking up electrons. These charges are usually insignificant as they are of low magnitude, and in most cases, they do not accumulate because they are about equally lost when people come in contact with conductors or grounded objects. The moisture present in atmospheric air is also a good conductor of electricity and contributes a lot to the leakage of charges from the human body. However, whenever atmospheric humidity is low, which is mostly during winter, the rate of electric leakage from the body by air moisture is significantly lower, and charges can accumulate up to voltages that are physically noticeable. Increased activities involving insulating objects including clothes, beddings, rugs, carpets, furniture and boxes can cause charges to build up. These materials act as capacitors and store electrons, which are later transferred to people who come in contact with them. When objects are moved across a carpet or rug, which are good electron givers, the objects become negatively charged with electrons, and people can pick up these electrons when they come in contact with the charged areas. When walking on a carpet or rug, electrons are sent up from the sole of the shoes to the skin, since humans are good electrical conductors. People that use clothed furniture can charge themselves up just by sitting on them. Wearing rubber-soled shoes across the floor also causes people to get charged.
While most static electricity events go unnoticed, sometimes charges accumulate up to significant voltages, which causes people to be exposed to very nasty incidents. Static shocks are perhaps the most prominent hazard of static electricity on people. These shocks happen when a charged person touches an electric conductor or someone else who is at a lower potential, and the built-up charges are released as an Electrostatic Discharge (ESD) or spark.
There are usually many occurrences of these ESD shocks during winter and dry weather, like someone getting zapped when trying to open a door, or when handling metallic objects. There are also many cases of ESD shocks experienced by drivers just after driving a car – this happens because the driving motion of the driver causes his clothing to rub against the fabric of the car seat, and electrons are sent up his body. If the driver had gained enough static charges, he would feel an electric shock when he reaches to close the metal car door. The feeling of shock is due to the stimulation of nerves when electrons are flowing out of the body.
Most people start feeling the zapping effect of electrostatic discharge at voltages between 3,000 to 3,500 volts. Walking over a carpet can generate up to 35,000 volts. These discharges are not life-threatening, but they can be very painful, and there have been reported cases of accidents that happened as a result of people’s reactions to static electric shocks, like someone recoiling from a shock while handling hot liquid. The touch from a charged person can also cause serious damage to sensitive electrical equipment; a simple touch from a charged person can damage an integrated circuit and is especially dangerous to the inner parts of computers. Static charges as low as 10 volts can cause significant hard drive damage and destroy microchips, but humans cannot perceive any static electricity less than 1,500 Volts.
The sparks generated from electrostatic discharge can cause ignitions or explosions if there is a presence of highly flammable gases and burnable materials like dust in the atmosphere. Although the probability of explosion from ESD is quite low (the sparks are usually very minimal and the natural air is not highly inflammable) there have, however, been cases of explosions from ESD, but mostly in industrial settings.
There is another physical effect of static electricity, which is not quite substantiated yet. There is a likelihood that static electricity can cause hygienic or physiological problems. The electric field around a person due to built-up static charges can cause a clinging effect with airborne particles. If a person is charged, he or she can attract oppositely charged particles in the air leading to plating out of atmospheric particles on the bare skin and clothes. Neutral particles can also get attracted by polarization, causing an atom’s neutral charge to be separated into two charged centers that hold a positive and negative charge, respectively. There are several speculations that if such particles are of irritating or allergenic nature, they can result in increased occurrences of skin diseases and irritation. This phenomenon is, however, a logical relation and is yet to be demonstrated.
There are many ways static electricity hazards can be avoided or prevented. Humidity is a huge factor in static electricity, as moisture present in the air is a good electric conductor and helps leak charges from the human body. In weathers where humidity is low, humidifiers can be used to raise air moisture content. Hard floors can be preferred to soft floors for much reduced static activities. Decluttering can also be done in homes to clear out capacitive objects, and soft furniture can be covered with leather. Materials that are prone to static activity can be treated with anti-static agents, which help to add a conductive layer to the surfaces of these materials. This ensures that excess charges are always spread out evenly. An application of anti-static agents like dryer sheets and fabric softeners in clothes dryers and washing machines helps to eliminate static cling. Electronic devices that are sensitive to static discharge can also be secured with antistatic bags. Anti-static mats can also be preferred to carpets and rugs to prevent the static charges from shuffling or walking, which is very common with carpets and rugs.
The effects of static electricity can be felt in a lot of ways, most of which go unnoticed by people. They can often pass as little painful experiences or nuisances when they re-occur frequently, but they can also potentially be of huge magnitude and can take a lot of effort and investment to prevent.