Electric current

What Is Electricity?

Electricity (or electrical energy) is the set of phenomena caused by the existence, interaction and movement of electric charges. That is, everything that causes the displacement of electrically charged subparticles (electrons or protons) through a conductor.

What is electricity?

Electricity can be analyzed from two perspectives:

  • Give yourself a macroscopic scale: what a person can observe.
  • From a microscopic scale: to be able to observe what is happening from a microscopic scale it is necessary to use special devices. The set of things that happen on a microscopic scale corresponds to what we can see on a macroscopic scale.

    From the macroscopic point of view, with the term electricity we refer generically to all large-scale physical phenomena involving one of the fundamental interactions: the electromagnetic force. Especially to electrostatic energy.

    From a microscopic point of view, these electrical phenomena are due to the interaction between charged particles on a very small scale, a molecular scale. We refer to protons in the nucleus of atoms or to ionized molecules and electrons. The typical macroscopic effects of such interactions are electric currents and the attraction or repulsion of electrical bodies or charges.

    Why is electricity important?

    Electricity is responsible for transporting energy from the point where energy is generated to the point where it is used. Thanks to electricity we have electricity and most of the appliances in our homes can be operated. Likewise, it is used in multiple industrial applications.

    This energy transport capacity has become the most widespread means of transport for energy in electricity grids. It is one of the most widespread means of transport for information in telecommunications (electrical communications).

    How does electricity contribute to climate change?

    Electricity is the ability to transport energy. According to this definition, they have no influence on climate change. However, it can help reinforce technologies that do influence climate change.

    If this form of energy transport did not exist, to heat our homes or to have electricity, we would need to burn coal, oil or gas. As we know, burning fossil fuels generates greenhouse gases that are harmful to the environment.

    On the other hand, electricity allows us to supply the electrical energy generated in renewable energy plants to our homes or in the industrial applications that are required. These renewable energy sources can be photovoltaic solar energy, wind power plants, hydraulic energy, etc.

    Types of electricity

    There are two types of electricity:

    • Static electricity. This type is produced by rubbing two or more objects and making friction
    • Dynamic electricity, which is the flow of electric charge through an electric field.

    Static electricity

    Static electricity is produced by accumulating electrical charges on the surface of a material. It is generally caused by rubbing materials. The result of a build-up of static electricity is that objects can be attracted to each other or even cause a spark to jump from one to the other.

    An example of static electricity is the result of rubbing a balloon with wool. After rubbing it, it remains slightly glued to the hand. The reason this happens is that the electrons in the wool are transferred to the balloon. The electrons have a negative charge, so that the balloon acquires a negative charge higher than the charge of the hand. At this time, we can say that the balloon is statically charged. The difference in charges generates an attraction between the balloon and the hand.

    Dynamic electricity

    Electric current is the rate of flow of electrons. Electric current is produced by moving electrons. Electric current intensity is measured in amps. Unlike static electricity, dynamic electricity must flow through a conductor. The current with electricity is the same as the current when you think of a river.

    With electricity, current is a measure of the amount of energy transferred over a period of time. That energy is called the flow of electrons. One of the results of the current is the heating of the conductor. When an electric stove heats up, it is due to current flow.

    What is an electric charge?

    Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge:

    • Positive electric charge, normally carried by protons.
    • Negative electric charge, normally carried by electrons.

    Similar charges repel each other and different charges attract each other. An object with no net charge is called neutral.

    Electric charge is a fundamental property associated with subatomic particles. This property follows the law of conservation of energy and determines its behavior in the face of electromagnetic interactions.

    An object equipped with an electric charge exerts a force at a certain distance on another object that has an electric charge. This concept can be compared to gravity, which makes one object attract another. However, gravity and electrical charges have two important differences:

    • Charges of the opposite sign attract each other while charges of the same sign repel each other. Gravity is always attractive, never repulsive.
    • The force of gravity is directly related to the mass of the objects in question, while the electric charge and the mass are not related when the objects are stationary.

    The total amount of electric charges remains virtually constant in the world. Since the two types of charge have opposite effects, the general normal result is electrical neutrality or apparent lack of charge. Therefore, in order to observe the effects of loading on fairly large amounts of material, it will be necessary to disturb the normal equilibrium and produce excess loading on the object in a desired manner.

    Electric charge on matter 

    Many solid substances have a crystalline structure, that is, their atoms are arranged in a regular three-dimensional grid. However, in some substances, the electrons surrounding these nuclei are not closely linked.

    Under certain conditions, it is possible to add or remove a good number of electrons without seriously disturbing the crystal structure. In other words, atomic nuclei tend to stay fixed in place, but electrons can often move. To give a negative charge, only excess electrons must be added. However, regarding positive and negative charges, it must be remembered that the plus and minus are indicative signs of an electrical state, not indicators of mathematical operations, as in arithmetic or algebra. When we see a negative sign applied to a charge, we must remember that it only indicates an excess of electrons and has nothing to do with subtraction.

    From an electrical point of view, it is possible to roughly classify all the substances that make up matter into two large groups. The types of substances that contain a relatively large amount of free electrons, which can move from one atom to another, are called electrical conductors. Substances in which the electrons are not free to move under moderate stress are called electrical insulators.

    Most metals are conductors of electricity, although differently from conductors used by the chemical sector, such as aqueous solutions of acids, bases or salts. On the other hand, most non-metallic substances are electrically insulating. There is no perfect conductor or perfect insulator, but in practice a number of substances serve this purpose very well. For example, silver, copper, aluminum, and even steel are often suitable as conductors, while glass, porcelain, most plastics, dry air, and wood are good insulators. In recent decades, the study of matter has led to the creation of materials that, under extreme conditions, manage to be superconducting.

    What is the electric field?

    The space around an electron or any other object that has an electric charge appears to be in a state of tension. This state is called an electric field. This is what interferes with the electric fields of other electrically charged objects and causes the mutual forces typical of such objects.

    If the electrons move, where they pass another field will be generated. This new field is called a magnetic field. The intensity of this field is directly proportional both to the number of moving electrons and to the speed at which they move, that is, to the electric current. This intensity is the current intensity and is measured in amps.

    Therefore, if a current is passed through a conveniently arranged set of copper wire coils, this wire coil will behave like a steel magnet. This new magnet will be able to attract or repel other similar coils of wire. Winding such a coil on an iron frame will reinforce the produced magnetic field. With all this, combining several coils of wire around an iron core, free to rotate, can obtain significant substantial mechanical forces.

    This device is called an electric motor. Today, electric motors operate all kinds of machinery, from the delicate exercises of the dentist to the gigantic machines of modern factories. There can be many electric motors in a modern house, from the oil boiler to the refrigerator, etc.

    How is electricity transmitted?

    Electricity can be transmitted by two types of electric current:

    In a direct current circuit the electrons always move in the same direction within it. An example of this circuit is given by any battery powered circuit, for example, a magnesium flash or an electrical system in automobiles. Sometimes, however, the current does not remain constant.

    Occasionally, numerous electrical circuits are used in which current regularly reverses the direction of its flow in the circuit. In this case, an alternating current circuit is obtained.

    The most common and used electrical circuits are alternating current. In an alternating current circuit the frequency, intensity of the current and the voltage of the circuit must be specified. Frequency measures half the number of times the current changes direction in one second.

    What is reactance?

    In alternating current circuits the current and voltage change. In these cases it is necessary to consider the effect of the reactance. As already mentioned, current always generates a magnetic field. When the current changes, the magnetic field caused by it also changes and this causes a counter electromotive force. Therefore, in an alternating current circuit, the applied voltage must overcome the opposition of the varying magnetic field, in addition to the common resistance of the circuit.

    The opposition encountered by alternating current is called inductive reactance. Inductive reactance is due to the change in its magnetic field. Electrons always repel each other, following the reciprocal action of their electric fields. Therefore, an electron moving in one conductor can force those in another to move. This is the case even if the two conductors are isolated from each other.

    Therefore, it can happen that an alternating current can flow even through a perfect insulator, while a continuum cannot. Of course, no electrons actually move through the insulator, but it is their interacting electric fields that cause the aforementioned displacements. This interesting effect is exploited in devices called capacitors, it is often used for alternating current circuits. Therefore, an alternating current can apparently flow through a capacitor, but not without encountering some opposition.

    The opposition to the flow of alternating current due to the action of the capacitor is called capacitive reactance. Inductive reactance, capacitive reactance, and resistance of a circuit are called, as a whole, the impedance of a circuit. By controlling the amount of inductive and capacitive reactance in a circuit, some interesting effects can be observed. One of the most important effects is resonance. Thanks to this effect, the circuit can be made to resonate, that is, crossed by an alternating current of a particular frequency, completely ignoring those of other frequencies that may also be present. It is thanks to the use of resonance that you can adjust the radio or TV on a particular broadcast station, excluding others.


    Published: May 20, 2019
    Last review: May 19, 2019