Electric current

Static Electricity

Static electricity

Static electricity is a set of phenomena associated with the occurrence, conservation and relaxation of a free electric charge on the surface or in most dielectrics or insulated conductors.

The electrification of dielectrics by friction can occur when two different substances come into contact due to the difference in atomic and molecular forces (due to the difference in the electron work function of the materials).

In this case, the redistribution of electrons (in liquids and gases also ions) occurs with the formation on the contact surfaces of the electrical layers with equal signs of electrical charges. In fact, the atoms and molecules of a substance, which have a stronger attraction, separate the electrons from another substance, creating a vortex movement of the ions in the medium in which they are closed.

The potential difference resulting from the contact surfaces depends on a number of factors: the dielectric properties of the materials, the values ​​of their mutual pressure on contact, the humidity and temperature of the surfaces of these bodies, and climatic conditions. In the subsequent separation of these bodies, each of them retains its electric charge, and with the increase in the distance between them due to the work in progress to the separation of charges, the potential difference increases and can reach tens and hundreds of kilovolts.

Electric shocks can form due to some electrical conductivity of moist air. With an air humidity of over 85%, virtually no static electricity is produced.

Examples of static electricity in everyday life

Static electricity is very widespread in everyday life. If, for example, a wool mat is spread on the floor, then by rubbing, the human body can receive a negative electric charge, while the mat will have a positive one. Another example is the electrification of a plastic comb, which, after styling, receives a negative charge and the hair receives a positive charge. The negatively charged accumulator is usually plastic bags, Styrofoam. The accumulator for an additional charge can be dry polyurethane polyurethane foam, if pressed by hand.

When a person's body is electrified it touches a metal object, such as a heating pipe or refrigerator, the accumulated charge will discharge instantly and the person will feel a slight electric shock.

Electrostatic discharge passes at very high voltage and extremely low currents. Even a simple combing of hair on a dry day can lead to the accumulation of a static charge with a voltage of tens of thousands of volts, but, the current of its release will be so small that it often cannot even be felt. They are the low values ​​of current that prevent a static charge from damaging a person when an instantaneous discharge occurs.

On the other hand, as voltages they can be dangerous for elements of various electronic devices: microprocessors, transistors, etc. Therefore, when working with electronic components, it is recommended to take measures to avoid the accumulation of static charge.

The lightning flashes of the thunderstorms

As a result of the movement of air currents saturated with water vapor, storm clouds are formed that are carriers of static electricity. Electric discharges form between clouds with opposite charges or, more often, between a charged cloud and the earth's ozone layer, followed by a discharge to the ground.

When a critical potential difference is reached, a lightning strike occurs between the clouds, on the earth, or in the near-cosmic layer of the planet. To protect against lightning, lightning arresters are installed that conduct the discharge directly to the ground.

In addition to lightning, storm clouds can cause dangerous electrical potentials in isolated metal objects due to electrostatic induction.

In 1872, an expedition led by geographer Henry Gannett was conquered by 13 of the height of the mountain of Montana (United States). It was given the name Electric Peak, as sparks from the fingers and hair on the head pioneering conquerors began to fall on top after a thunderstorm.

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Last review: January 23, 2020