2 OBJECTS CAN AFFECT OTHER OBJECTS AT A DISTANCE

Electricity

Electricity is a form of energy, that manifests either as static electricity at a certain point or as an electric current that passes material from one place to another.

Static electricity

Static electricity arises, for example, when you rub one thing against the other. For example, if you rub the balloon on your hair, the hair will then be attracted to the balloon. This is because the friction arises on both surfaces with the opposite electrical charge (a small amount of electricity), which is reflected by the heavier balloon attracting lighter hair, if we keep the balloon in hand.

A similar phenomenon can be observed if we walk the nylon carpet. While walking, we rub feet against the carpet, our body is gradually charging an electric charge and if we touch, for example, metallic door handle, we feel „kicking“, which is a sense of electrical discharge, in which the electrical charge collected is discharged by ground. If we touch the door handle in the dark, we can even see the discharge in the form of a tiny „lightning“ that jumps between the hand and the handle before touching it. This means that static electricity is also manifested remotely.

Lightnings

Flashes observed during the storm in the sky are also a manifestation of static electricity. The clouds (condensed water in the atmosphere) move through the air, rubbing the surrounding air and charging the electric charge. When the electrical charge obtained is large enough, it jumps to the Earth in the form of lightning. Sufficiently sensitive people even feel in the air sort of gentle shaking, or ticking if the storm is nearby. Electric lightning discharges have enormous dimensions, which is a manifestation of the enormous amount of electrical energy accumulated, as well as a sign of the enormous distance the electric charge is causing

Electricity

Electricity is caused by electrons. Electrons are particles of the atom that „circle „ at the edges of the atoms from which all materials are formed. Each electron carries a negative charge. The atoms themselves usually have a balanced number of positive charges (in the nucleus of the atom) and negative charges (in the atom shell), they are electrically neutral, have no electrical charge. Substances, such as the rubber from which the balloon is made, consist of molecules and those of individual atoms. Since atoms do not have an electrical charge, molecules that are made up of atoms do not have them, so the substance itself, in our case the rubber from which the balloon is made, does not have an electric charge.

But if we start rubbing a balloon against another material back and forth, the electric charge begins to form. By pushing and pulling our hands, some electrons are released from the surface of the balloon and attached to the surface of the material, for example hair. This will make the balloon itself miss the electrons and become positively charged (gaining a small positive electric charge). On the contrary, our hair contains more electrons than usually and thus gain a small negative electric charge. As the positive and negative electric charges (like the opposite magnetic poles) attract each other, the balloon attracts hair to itself. This attractive force operates at a certain distance.

To create electric charges it is not enough just to rub two objects against each other, more important is to rub two different materials. By rubbing two different materials against each other, an electric charge arises due to a phenomenon called triboelectric (or triboelectric effect).

As already mentioned, all substances are composed of neutral atoms. Different substances are composed of different molecules, which are formed by different but always neutral atoms. In molecules of different substances, the electrons of the individual atoms are attracted by a great deal of force, depending on what chemical bonds are present in the individual molecules between the atoms. Thus, when rubbing two materials against each other, electrons that are weaker bounded in one substance may become loose and pass into the surface of the other substance in which the electrons are attracted more strongly. As a result, one material is charged positively (the one that loses the electrons) and the other is negatively (one that receives the electrons). This electrifies the materials and creates static electricity. Longer friction of materials increases the number of atoms involved in this electron transfer, increases the electric charge of the rubbed materials and thus increases the generated static electricity.

Pic 11: Tribolelectric series

As a result, the positive charging is typical for some materials and the negative charge for others. Also, how much electric charge we get depends on the rubbed material – some substances are electrified more and other less when the same friction occurs. Based on this knowledge, it is possible to arrange the materials according to the „charge ability“ during the friction. This kind of substance arrangement is called triboelectric series (on the picture).

It is important to note that this currently accepted explanation for the emergence of static electricity was disrupted by a series of researches in 2011 where scientists found that static electricity is not just a simple electron exchange from one substance to another, but a chemical reaction that takes place at touching two surfaces. The starting point for their exploration and returning to the theory of static electricity was the fact that static electricity can also be generated by contacting the same two materials, and even enough to touch (lie on) for some time without rubbing. However, the new explanation has not yet been specified in a compact theory that would replace the currently accepted one we have stated. This implies an important feature of scientific theories – they are not final, are object to constant scrutiny and the development of the means of science is continually being improved.

Using static electricity

Even though static electricity seems to be quite unrecoverable compared to electric current, man uses it in different devices. On the principle of static electricity, for example, laser printers and copes work. Static electricity is transmitted by toner particles from the cylinder to the paper. Herbicide atomizers work on the principle of static electricity to ensure that herbicides reach the entire surface of the leaves of plants that need to be discarded. Also, automatic coloring and painting robots in car production factories use static electricity to make the droplets of paint and varnish only on car bodywork and not on other devices around. Static electricity is often used in various air filters to remove small impurities from the air.

On the other hand, static electricity can also cause serious problems, such as working with small electronic components. Knowledge of the principle of the emergence and demise of static electricity helps engineers design antistatic solutions in places where static electricity is undesirable.

Electrical stream

In addition to static electricity we also know electricity in the form of electric current. When a substance electrons move from one place to another, we say that it flows through an electric current. In this case, electrons are carriers of electrical power.

To understand the difference between static electricity and electric current, it is good to know the difference between potential and kinetic energy. Simply, potential energy represents energy that is in some way stored for its later use. For example, a car standing on the hill has potential energy because it has the potential (option) to roll down the hill. By moving downwards the hill, its potential energy is transformed into a kinetic (energy that the object has as it moves).

Static electricity and electric current can be compared to potential and kinetic energy. When static electricity arises, it has the potential to manifest itself in the future. The electricity stored in the battery represents potential energy. The energy stored in the battery can be used for example for lighting the bulb in a torch. When you turn on the torch, the battery inside will provide the power to the bulb and turn it into light energy (that is, battery power is consumed – it turns into light). As long as the flashlight is turned on, the battery will provide the light bulb with power until the moment when the electrical energy stored in the battery is not spent.

Electrical circuit

To produce electric current, we need to create an electrical circuit. The electrical circuit must be closed, with electrical appliances being connected to the energy source (battery) with the appliance (for example, a light bulb in a torch) using conductive cables. The electrical current flows only when the circuit is closed – the cable (driver) connects the battery with the bulb and back the bulb with the battery. The closure of the electrical circuit must also be ensured within appliances such as bulbs. The light bulb shows how one wire enters the bulb (No. 8) and the other one exits it (No. 11). If we connect the bulb with wires to the power supply (battery) only by connecting a metal thread (No. 9) into which only one part of the circuit (No. 8) opens within the bulb, the electric circuit will not be closed because the other end of the circuit within the bulb (No. 11) remains open and the bulb does not light up.

Pic 12: Electrical circuit

From the practical point of view, the switch is added to the electrical circuits. It is a device by which we break the electrical circuit. When the electrical circuit is interrupted, the electric current stops flowing and the bulb does not light.

Electrical circuit conductors and insulators

Materials that conduct electrical current are called conductors. Those that do not conduct electric current are called electrical insulators. The best electric current conductors are metals (gold, silver, copper, aluminum, nickel, iron, etc.). All metals conduct electric current. Graphite (pencil lead), human body, salt water (but also other aqueous solutions) and other substances also conduct electric current. Electrical insulators (non-conductors) include, for example, rubber, various plastics, wood, paper, wax, glass and porcelain, and others. Since the electric current is the electron current, this phenomenon can only be observed in materials whose structure allows the free movement of electrons. Therefore, metals are the best electric current conductors. This materials are called materials of high conductivity.

Electrical magnet

Electrical and magnetic phenomena are linked together. For example, we meet with the use of the so-called electromagnets. An electromagnet is a steel whose magnetic property can be switched on or off by electric current. They are used for example on boneyards. If we want to lift the car, we approach the electromagnet, we turn the electric current and the electromagnet will attract the wreck. We transfer it to the desired location and when the electric current is switched off, the magnetic property is lost and the electromagnet is separated from the wreck. Electromagnets operate on the fact that the electrical conductors in the vicinity of the electric power are generated by a magnetic field. This can be seen, for example, by placing a compass nearby any electrical cable, and when turning the electric current in the cable, the compass‘s needle is deflected. The magnetic field arises as a result of the change in electrical current. Electric motors are also working on this principle. An electric motor is a device that changes electrical energy to mechanical energy. The electrical power of the engine and the motor moves the whole mechanism to which the engine is connected.

Eletric motor

The electric motor consists of a cylinder in which magnets are located at its edge. There is a steel core in the center of the cylinder, which is multiplied by an electric cable (for example, copper wire). When the power is released into the cable, the steel core becomes magnetized due to the presence of a magnetic field generated by the current flowing through the cable. The magnets that are located at the edge of the cylinder cause the electromagnet (steel core) to be attracted and repelled in the center, thereby rotating the steel core of the engine, as well as other components of the device attached to the engine.

Dynamo

When we can create a magnet by means of electricity, we can also generate electricity through magnetism. Dynamo is a device similar to an electric motor. When we rotate the pedals on a bicycle, the dynamo that is pinned on the wheel axis also rotates. Inside the dynamo there is a steel core, which, like the electromagnets, is wrapped with multiple electric cables. The steel core moves between the magnets, creating an electric current, and we can, for example, light up the bicycle light. Similarly, electricity generation in power plants also works, the only difference is in the energy we use to spin the steel core in dynamo. It may be, for example, wind or water, which rotates the core of the electric generator (dynamo), but also water vapor. In principle, almost all power plants produce electricity in the same way. Solar power plants are an exception. When the light falls on a solar cell, the material from which it is made (silicone) captures the energy of the world and transforms it directly into electrical energy. Since energy leaks are minimal in such devices, solar cells are considered to be highly efficient compared to electrical generators.