Study Material

# Static electricity

We explain what static electricity is, how it is produced, the effects on the body and we give several examples

## What is static electricity?

The static electricity is a natural phenomenon that occurs when a material has lost or gained electrons. It happens frequently in insulators, but metals can also retain electrical charge at times.

It is a temporary situation, since the charge imbalance is reestablished shortly, when the charged material gives up the excess electrons or takes electrons to regain neutrality.

The phenomenon of static electricity is closely linked to the structure of matter . The atoms of any substance, be it gas, liquid or solid, consist of a nucleus of positively charged protons and uncharged neutrons, orbited by negatively charged electrons.

Materials are generally in a neutral state, but occasionally, through contact with other materials, they can lose or gain electrons, causing them to be left with a net positive or negative charge.

Static electric charges are governed by a fundamental principle: charges of opposite signs attract and charges of the same sign repel .

Then, if a charged material comes into contact with another that has a charge of the opposite sign, a temporary attraction occurs, or a spark appears, as a consequence of the transfer of electrons, which tends to restore the neutrality of the materials.

## How is static electricity produced?

It is common for friction or friction between two materials of different nature to be the cause of static electricity, as will be seen later in the examples section. In this way, some materials will give up electrons and others will gain them, thus generating a net static charge on each one.

Apart from friction there are other ways to produce static electricity.

### Electrification by contact and induction

An object can be electrified by direct contact with another charged object. And if there is no direct contact, but a close-up, objects can still be charged by induction.

But if the neutral metal is approached by a negatively charged object, the effect will also be of attraction, because the electrons of the metal will be concentrated in the farthest part, leaving the nearby region with a negative charge deficit, that is, positive charge.

## E static LECTRICITY in the body and its effects

The body can act as a capacitor and accumulate static electricity. When sufficient charges have accumulated, contact with the water contained in the air, which is a good insulator, produces the discharge, as long as the humidity percentage is adequate.

But if this percentage is low and the air is very dry, the charges continue to accumulate without the person noticing, until it occurs to him to touch a metallic object such as a door knob, a car door or even another. person. The discharge produces an unpleasant tingling sensation that may cause a startle.

### Factors that affect the accumulation of charges

People accumulate static charge thanks to factors such as:

• The way you walk or move and the kind of pavement
• Shoe sole type
• Make contact with easily electrically charged bodies or electric fields of a certain intensity.
• The degree of moisture in the skin
• The percentage of ambient humidity
• Use of synthetic fiber-based clothing, as well as rubber gloves and footwear.

### Risks

Apart from the unpleasant sensation produced by the shock, the risk is not excessive on a daily basis, although people who use pacemakers should be vigilant.

However, for those who work with easily ignitable substances, special precautions must be taken to avoid accidental explosions and fires.

There is also the risk of tripping, falling or making a mistake when operating machinery, after the operator receives the shock.

On the other hand, static electricity causes dust to accumulate that clogs ducts and filters, causing numerous inconveniences in the operation of machinery and malfunctions in electrical and electronic parts.

## Examples of static electricity

### Sheets

Sometimes sheets of paper that pass through the printer mechanism stick together. It is due to the friction between the sheets and the rollers of the printers, when when they rub, electrons of the material with which the rollers are made pass to the paper and vice versa.

### Clothes in the dryer

If freshly washed clothes are put to dry in the electric dryer without fabric softener, shirts and socks tend to stick. When they are detached, clicks are heard and again, the culprit is friction, which separates electrons from some fabrics and causes them to pass to others.

### Amber

By rubbing a piece of amber with a woolen cloth, it is able to attract small pieces of paper, just like a comb that has been passed through the hair

### Automobiles

Cars can accumulate electrical charge. Insulators have already been seen to charge and retain charge, but metals can also do so if they are insulated from the ground, and the car’s wheels are made of rubber. A person who touches the charged sheet metal continues the circuit to ground and perceives a brief electric shock.

### The photocopier

The copier paper is statically loaded with a loading pattern that duplicates the image to be copied. The carbon used in the ink has a charge of the opposite sign, so it adheres to the pattern of the paper to form the image.

### Laser printer

The image pattern is formed on a printer’s light-sensitive drum, which is illuminated with a laser beam.

The drum rotates and the laser beam illuminates certain areas, in accordance with the pattern of the image, and in doing so, it gives them a negative charge. For its part, the toner is a graphite powder with an electro-positive tendency, which adheres to the pattern created by the laser on the drum, after which the powder is transferred to the paper to form the image.

### Spray paint

In a spray gun for painting, each drop of paint is positively charged so that they repel each other, making it easier for them to spread over the surface to be painted and do so more evenly. If the surface to be painted is metallic, then it is negatively charged so that the paint droplets are attracted to the surface.

### Clouds

In the clouds there are drops of water and dust particles, which are constantly stirred by the wind. The constant collisions cause the electric charges to separate, occupying different regions of the cloud, but the same friction of the air then prevents the different charges from attracting each other.

When a critical charge is finally reached, an electrical discharge occurs between the clouds and the Earth, which by the way is also conductive. From the Earth to the clouds, channels are also opened through which charges circulate, which interact with air molecules at high temperature, producing lightning. The shock wave generated is what produces the thunder boom.

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