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Today we are going to review electricity.

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You should understand everything because we are going to study electricity this year in this course but a little bit more complicated.

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So it's very important that you have learned the contents of the first episode in order to improve

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them and reach the level of the second episode. So this is the main reason why we are going to

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review these contents. This is the list of things that you should

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study and you should review. I strongly believe that all of them know all of

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them so I think it's just only to remember these contents.

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Matter is a mixture of different things, indeed it is not homogeneous, indeed it is heterogeneous.

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And its components are composed of put components that are formed by molecules.

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The molecules can be obtained by combining, by linking the different atoms in more or less defined proportions.

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The atoms are composed of a shell with electrons, particles with mass and negative charge, and a nucleus consisting in protons, particles with positive charge and mass, and neutrons, particles that only have mass.

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So, therefore, the mass and the church are intrinsic characteristics of the matter itself.

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And we also know that between two masses there are always attractive forces,

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But, on the other hand, between two churches we can have attractive if the churches are of different signs

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or repulsion if the churches are opposite signs.

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But electrical current is indeed the movement of electrical charge, so taking into consideration

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that electrical charge is just only a characteristic of the matter, you need something, a carrier

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for this characteristic and the carrier can be, for example, electrons that we have already

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described in this presentation, but we can also have other kinds of carrier.

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One of these kind of carriers could be holes.

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Holes are when you lose an electron.

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If you haven´t an electron you have a hole and a hole is a carrier of a positive charge.

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And finally, you can also carry an electric charge using ions.

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The ions are the result of an atom which has more electrons than an atom.

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So negative electricity charge and they are called cations, sorry, anions, or they can

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have less electrons than neutral atoms.

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In this particular case, they are called cations.

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Apart from this, matter can be insulator or insulators or conductors.

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They are conductors if they let that the charge move into themselves, if they don't allow

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the movement of the electrical charge, they are insulators and it's very difficult to

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establish a limit between insulators and conductors. So a substance could also be

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semiconductor. Well, if we want to study the movement of the electrical

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church you need to know the principal electrical magnitudes. This slide shows them.

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You can see the definition of the magnitudes, the mathematical formula and the unit and the symbol.

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Between them there are three which are the most important, which are intensity, the charge per unit of time,

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the unit of intensity is amperio,

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and the voltage, which is the energy you have to use to move a charge between two points in the electrical field

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which unit is Volt, and a resistance, which is the opposition of the material, of the matter, to the current, to the movement of charge, and its unit is Ohm.

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There are also others important, such as electrical energy, which unit is J, and electrical power, which unit is V.

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And I think you should study very carefully and if you have any doubts you should tell me in order to explain it more.

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But I think all of you have known all these electrical magnitudes.

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So, electric circuits transform electrical energy into other kinds of energies

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and it needs different parts, it needs different components, physical components that you can touch, something, hardware that you can touch.

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So these components, these parts of circuits can be classified into four main groups

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which are generators, it provides energy, electrical energy

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active elements, which transform electrical energy into other kinds of energy

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controls and maneuvers which are responsible for the manipulation of the circuit,

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protection elements and cables.

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Here you have a list of different elements but obviously

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and they are their symbols, because symbols for electrical components have been known,

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have been studied, because it's an universal language.

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Here you can see, for example, pulp, which is light pulp, is very interesting, very important.

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You also have, for example, batteries, which gives you power, and different kinds of input

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devices, which are switches, different switches, that you can see some of them

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and others. Motor, it is important also, fuse, it's important to study these

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symbols. Well, as I said before, the three more important electrical magnitudes

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are voltage intensity and resistance ohms show that the relationship between

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these three magnitudes is that the slide show it is voltage is the

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multiplication of resistance and intensity and this law is very important

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because we can use it for all of the different exercises in electrical circuits.

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The slide shows the simplest exercise you should solve.

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In it you have a battery of 5 volts and a light bulb and it also shows an emitter and a voltmeter.

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The emitter measures the electric intensity, which is 50 milliamperes.

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So, by using Ohm's law, you can calculate the value of the resistance, as you can see here in this image.

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So, it's very important to understand this exercise because we will use and we will solve exercises a little bit more complicated in this level.

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Finally, we are going to revise other effects which are associated with circuits, electrical circuits.

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One of them is Joule's effect. Joule's effect is a consequence of the resistance of the materials.

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and it consists in the transformation of part of the electric energy into heat

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And this energy loses and you can't use this energy. So it seems to be a negative effect.

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Apart from Joule's effect there are two other effects which are very interesting.

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One is the creation of magnetic fields because of the movements of electric charge.

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and other is the production of electric current because of the movement of the changes in the time of some magnetic flux.

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Both of them are used in electric machines, motors, generators and so on.

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And we will study them this year.

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And this is the end of the review of electricity and I hope it is useful. It could be useful.