Static Electricity

Did you know that the Ancient Greek name for amber is elektron? What does that have to do with electricity? Back in 600 BC the Greek mathematician Thales noticed that a piece of amber rubbed with wool attracts dust crumbs and cat hair. This is perhaps the earliest recorded example of an observation of the effects of static electricity. Static electricity is caused by a disproportionate amount of negative and positive electric charges inside or on the surface of a substance. The fact that objects rubbing against each other sometimes attract and sometimes repel other objects lead Thales and the philosophers of that period to realize that there could be two kinds of electric charge.

The naming of the electric charges discovered in 600 BC took place approximately 2300 years later. The positive and negative names of electric charges were given by Benjamin Franklin in the 1700s. Franklin suggested that the charge of the plastic rod be called negative and the charge of the glass rod positive. In the following years, in the light of developments in physics, the nature of electric charges has been learned definitively.

Benjamin Franklin

Atoms, which are the basic building blocks of ordinary matter; consist of protons, neutrons, and electrons. Protons and neutrons that make up the nucleus are of interest to nuclear physics. A large amount of energy is required to separate these particles from each other. The situation is different for electrons circulating around the nucleus. It is much easier to remove an electron from an atom or to take an electron from an atom, compared to removing a proton from the atomic nucleus.

Atoms, and therefore matter made up of atoms, tend to be neutral. The atom balances the positively$(+)$charged protons in the nucleus with negatively$(-)$charged electrons that orbit the nucleus. An imbalance in electric charge occurs when the number of electrons is more or less than the number of protons. If the number of electrons is more than the number of protons, the charge is negative, and if it is less, the charge is positive. The SI unit of electric charge is Coulomb$\left(\mathrm{C}\right)$. The smallest charge found in nature is the charge of the electron. Therefore, an electron charge is defined as an elementary charge or a unit charge.

Static Electricity Examples

The gain or loss of electrons by an atom is called charging. Atoms can gain or lose electrons in different ways. As a result, substances can be electrically charged in different ways.

When neutral (uncharged) objects are brought close to each other, no attraction or repulsion is observed.

When uncharged objects are brought near each other, they do not attract or repel one another, StudySmarter Originals

Electron exchange takes place between the objects that are rubbed against each other. While an excess negative charge occurs in the object that receives electrons, the negative charge decreases in the object that donates electrons. An excess positive charge occurs in the electron donor body, and an excess negative charge occurs in the electron acceptor body. As in the example that uses wool fabric and a plastic rod, the electron donor object is positively charged, and the receiving object is negatively charged. Objects charged by friction are charged with equal and opposite electric charges. The electron-accepting object is charged with a$-q$charge, while the electron-donating object is charged with a$+q$charge. The sum of the charges before and after the rubbing of the objects is equal due to the conservation of charge.

Electrostatic forces are non-contact forces. When two plastic rods rub against a piece of wool or two glass rods rubbed with silk cloth are brought closer together, the rods repel each other. This experiment shows that objects charged with the same electric charge repel each other.

When two plastic rods rub against a piece of wool or two glass rods rubbed with silk cloth are brought closer together, the rods repel each other, StudySmarter Originals

When the plastic rod that has been rubbed against the wool fabric and the glass rod that's been rubbed against the silk fabric are brought closer together, they attract each other.

Plastic rods and glass rods attract each other when they are rubbed on wool and silk fabric respectively. StudySmarter Originals

A similar phenomenon is observed when rubbing together wool fabric and a plastic rod, or silk fabric and a glass rod. This shows that objects charged with opposite electric charges attract each other. Due to the repulsive force and the attractive force exerted by the objects on each other, we can be sure that two types of charge must exist.

Objects charged with opposite electric charges attract each other, StudySmarter Originals

The result of this experiment can be summarized as follows: Charged objects with the same electric charge repel each other, and charged objects with opposite electric charges attract each other.

Uses of Static Electricity

Static electricity is a part of our daily lives. Static electricity is used for pollution control, air cleaning, and the development of technological devices. For example, in photocopying, air filtering for factories, car painting, and mobile phones, static electricity can be used.

Uses of Static Electricity: Pollution control

One particular use of static electricity is to use it to control levels of pollutive particulate matter which could be harmful to humans or more broadly to the natural environment. Two applications of this particular use of static electricity for pollution control are explained below.

Uses of Static Electricity: Electrostatic precipitators

Electrostatic precipitators are one example of the varied uses of static electricity that can be used for pollution control via the application of static charge to attract the particles in the air and collect them. Many power plants use fossil fuels like coal and oil to generate electricity. When these fuels burn, they emit smoke. Smoke contains microscopic solid particles, such as unreacted carbon, which can cause structural damage and respiratory problems. To avoid this, the smoke from waste gases is eliminated before they exit the chimneys. This work necessitates the use of an electrostatic precipitator.

The electrostatic precipitator removes tiny particles from the air by forcing them to become charged then attracted to metal plates. Wikimedia Commons

Uses of Static Electricity: Air fresheners

Air may be purified using static electricity. Static electricity is used in air purifiers to change the charges in dust particles so that they attach to a plate or filter of the purifier that has the opposite charge as the dust. These charged particles are drawn to a plate on the device with the opposite charge and attached to it.

Uses of Static Electricity: Photocopiers

In photocopiers, a drum or belt is coated with a layer of photoconductive material. When light is incident on a photoconductive substance it will begin to conduct electricity. When a copier shines light onto a piece of paper on the glass surface, static electricity projects a pattern of the image onto the positively charged photoreceptive drum below. When light reflects from blank spaces on the page, it strikes the drum, neutralizing the charged particles that coat the drum's surface. Positive charges are only left on the paper when there are dark spots that do not reflect light. Negatively charged toner is attracted to these positive charges. The toner is then transferred to a positively charged sheet of paper and fused together.

A printer is an example of the many and varied uses of static electricity in our daily lives

Electrostatic painting

Electrostatic painting processes are also known as powder painting among the general public. Car bodies are most often painted using electrostatic painting techniques. The principle that opposite charges attract each other is the basic concept behind this process. Electrically charged coloured powder particles adhere to the surface to be painted electrically and stick to the surface completely due to the subsequent firing processes.

Electrostatic painting is based on the principle of static electricity

Uses of Static Electricity: Mobile phones

Most smartphones use capacitive touch screens, which are made of materials such as copper or indium tin oxide and store electrical charges in an electrostatic grid of tiny wires, each thinner than a human hair. When a finger touches the screen, a small amount of electrical charge is transferred from the finger to complete the circuit, resulting in a voltage drop at that location. The program analyses the location of the voltage drop before taking a particular preprogrammed action.

A smartphone with a touch screen is also an example of the uses of static electricity

Dangers of Static Electricity

In tankers carrying flammable liquids, static electricity charge accumulates due to the agitation of the liquid in the tank caused by movement as well as friction with the surrounding air. It is necessary to use a grounding chain in order to prevent this static electricity charge from reaching dangerous levels. The grounding chain allows the built-up static electricity to discharge safely into the ground.

A truck carrying flammable liquid can be very dangerous if not taken care of properly. That's why you can see a warning signs indiciating that you shouldn't smoke cigarretes or light flames within the vicinity of the tanker.

Dangers of Static Electricity: Bolts of Lightning

Particles within clouds are charged as a result of collision and friction. These particles cause the upper part of the cloud to acquire a purely positive charge and the lower parts of the cloud to become negatively charged. As a result, the soil under the clouds is charged with the opposite charge; that is, positively. The separation of negative charges in the clouds and positive charges on the ground continues for a period of time. The insulating air between the cloud and the ground begins to become conductive, and as the potential difference between the cloud and the ground increases, it becomes easier for a current to pierce the air. With the puncture of the air, the high voltage in the cloud is discharged to the ground. A current between 2,000 and 200,000 amperes flows in these lightning discharges.

Dangers of Static Electricity: Aircrafts

Electricity on the outside of aeroplanes is formed in 3 different ways. Electricity generated by a lightning strike during flight, static electricity generated by friction as the aircraft passes through snow, ice, hail, or dust clouds, and static electricity generated by electronic devices. This static electricity generated on the aircraft is distributed by the pointed metal protrusions on the wingtips of the aircraft. If static electricity circulating in the fuselage of the aircraft was to be momentarily released into the air, it could explode due to the severe discharges that may occur while the aircraft is landing.

Static Electricity in the Body

Electric shocks in the body can be caused by the sudden exposure of the body to electricity. When touching an object or making hand contact with someone, crackling sounds are sometimes heard and a sharp 'jolt' can be felt. This is a situation that almost everyone experiences at some point in their lives. Sometimes when shaking hands with someone and sometimes when a door handle is grasped, crackling sounds are heard and the body experiences a momentary electric shock. The excess static electricity accumulated in the body is discharged, causing a feeling of instant electric shock in the persons body.

Due to static electricity, a repulsive force occurs and the hair stands out away from the head.