The physics of electricity is what each of us has to deal with. In the article we will consider the basic concepts associated with it.
What is electricity? For an uninitiated person, it is associated with a flash of lightning or with the energy that feeds the TV and the washing machine. He knows that electric trains use electrical energy. What else can he talk about? Power lines remind him of our dependence on electricity. Someone can give some other examples.
However, many other, not so obvious, but everyday phenomena are connected with electricity. Physics introduces us all to them. We begin to study electricity (tasks, definitions and formulas) back in school. And we learn a lot of interesting things. It turns out that a beating heart, a running athlete, a sleeping child and a swimming fish - all produce electrical energy.
Electrons and Protons
Define the basic concepts. From the scientist's point of view, the physics of electricity is associated with the movement of electrons and other charged particles in various substances. Therefore, a scientific understanding of the nature of the phenomenon of interest to us depends on the level of knowledge about atoms and their subatomic particles. The key to this understanding is a tiny electron. Atoms of any substance contain one or more electrons moving in different orbits around the nucleus, just like planets orbiting the sun. Usually the number of electrons in an atom is equal to the number of protons in the nucleus. However, protons, being much heavier than electrons, can be considered as if fixed in the center of an atom. This extremely simplified model of the atom is quite enough to explain the foundations of such a phenomenon as the physics of electricity.
What else do you need to know? Electrons and protons have the same electric charge (but of different signs), so they are attracted to each other. The proton charge is positive, and the electron is negative. An atom that has more or less electrons than usual is called an ion. If there are not enough of them in an atom, then it is called a positive ion. If it contains their excess, then it is called a negative ion.
When an electron leaves an atom, it acquires a certain positive charge. An electron, devoid of its opposite - a proton, either moves to another atom, or returns to the former.
Why do electrons leave atoms?
There are several reasons for this. The most common is that under the influence of a light pulse or some external electron, an electron moving in an atom can be knocked out of its orbit. Heat causes atoms to oscillate faster. This means that electrons can fly out of their atom. In chemical reactions, they also move from atom to atom.
Muscles give us a good example of the relationship between chemical and electrical activity. Their fibers contract when exposed to an electrical signal from the nervous system. Electric current stimulates chemical reactions. They also lead to muscle contraction. External electrical signals are often used to artificially stimulate muscle activity.
Conductivity
In some substances, electrons move more freely under the action of an external electric field than in others. Such substances are said to have good conductivity. They are called conductors. These include most metals, heated gases and some liquids. Air, rubber, oil, polyethylene and glass do not conduct electricity well. They are called dielectrics and are used to insulate good conductors. Ideal insulators (absolutely not conducting current) do not exist. Under certain conditions, electrons can be removed from any atom. However, usually these conditions are so difficult to fulfill that, from a practical point of view, such substances can be considered non-conductive.
Getting acquainted with a science such as physics (section "Electricity"), we learn that there is a special group of substances. These are semiconductors. They behave partly as dielectrics, and partly as conductors. These include, in particular: germanium, silicon, copper oxide. Due to its properties, the semiconductor finds many uses. For example, it can serve as an electric valve: like a bicycle tire valve, it allows charges to move in only one direction. Such devices are called rectifiers. They are used in miniature radios and in large power plants to convert AC to DC.
Heat is a chaotic form of the movement of molecules or atoms, and temperature is a measure of the intensity of this movement (in most metals, the movement of electrons becomes more free with decreasing temperature). This means that the resistance to the free motion of electrons decreases with decreasing temperature. In other words, the conductivity of metals increases.
Superconductivity
In some substances, at very low temperatures, the resistance to the flow of electrons disappears completely, and the electrons, having started the movement, continue it unlimitedly. This phenomenon is called superconductivity. At a temperature of several degrees above absolute zero (- 273 ° C), it is observed in metals such as tin, lead, aluminum and niobium.
Van de Graaff Generators
The school curriculum includes various experiments with electricity. There are many types of generators, one of which we would like to talk more about. The Van de Graaff generator is used to produce extra high voltage. If an object containing an excess of positive ions is placed inside the container, then electrons will appear on the inner surface of the latter, and the same number of positive ions will appear on the outer surface. If you now touch the inner surface of a charged object, then all free electrons will pass onto it. On the outside, positive charges will remain.
In the Van de Graaff generator, positive ions from the source are deposited on a conveyor belt passing inside a metal sphere. The tape is connected to the inner surface of the sphere using a conductor in the form of a ridge. Electrons flow from the inner surface of the sphere. On its outer side, positive ions appear. The effect can be enhanced using two generators.
Electricity
The school course in physics also includes such a thing as electric current. What is it? Electric current is caused by the movement of electric charges. When the electric lamp connected to the battery is turned on, current flows through the wire from one pole of the battery to the lamp, then through its hair, causing it to glow, and returns back through the second wire to the other pole of the battery. If you turn the switch, the circuit will open - the movement of current will stop, and the lamp will go out.
Electron motion
The current in most cases is an ordered movement of electrons in a metal that serves as a conductor. In all conductors and some other substances, their random movement always occurs, even if the current does not flow. Electrons in matter can be relatively free or strongly bonded. Good conductors have free electrons that can move. But in poor conductors, or insulators, most of these particles are firmly bound to atoms, which impedes their movement.
Sometimes the movement of electrons in a certain direction is created naturally or artificially in a conductor. This stream is called electric current. It is measured in amperes (A). Carriers of current can also be ions (in gases or solutions) and “holes” (lack of electrons in some types of semiconductors. The latter behave like positively charged carriers of electric current. To force electrons to move in one direction or another, some force is needed. In nature its sources may include: exposure to sunlight, magnetic effects, and chemical reactions, some of which are used to generate electric current, typically for this purpose a generator using magnetic effects, and an element (battery), the action of which is caused by chemical reactions. Both devices, creating an electromotive force (EMF), cause the electrons to move in one direction along the circuit. The value of the EMF is measured in volts (V). These are the basic units of measurement of electricity.
The magnitude of the EMF and the current strength are interconnected, like pressure and flow in a liquid. Water pipes are always filled with water under a certain pressure, but water starts to flow only when the tap is opened.
Similarly, an electric circuit can be connected to an emf source, but the current will not flow in it until a path is created along which electrons can move. It can be, say, an electric lamp or a vacuum cleaner, the switch here plays the role of a crane that "releases" current.
The relationship between current and voltage
As the voltage in the circuit increases, so does the current. Studying the course of physics, we learn that electrical circuits consist of several different sections: usually a circuit breaker, conductors and a device - a consumer of electricity. All of them, connected together, create resistance to electric current, which (under the condition of constant temperature) for these components does not change with time, but for each of them is different. Therefore, if the same voltage is applied to the light bulb and to the iron, then the flow of electrons in each of the devices will be different, because their resistance is different. Consequently, the strength of the current flowing through a certain section of the circuit is determined not only by the voltage, but also by the resistance of the conductors and devices.
Ohm's law
The value of electrical resistance is measured in ohms (ohms) in a science such as physics. Electricity (formulas, definitions, experiments) is an extensive topic. We will not derive complex formulas. For the first acquaintance with the topic, what was said above is enough. However, one formula is still worth deriving. She is very uncomplicated. For any conductor or system of conductors and devices, the relationship between voltage, current and resistance is given by the formula: voltage = current x resistance. This is a mathematical expression of Ohm's law, named after George Ohm (1787-1854), who was the first to establish the relationship between these three parameters.
The physics of electricity is a very interesting branch of science. We examined only the basic concepts associated with it. You have learned what electricity is, how it is generated. We hope you find this information useful.