Luyện nói tiếng Anh bằng Shadowing qua video: Concept of Electric Current with Train example | TheElectricalGuy
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Hello everyone, in this video we are going to learn about all of these Topics.
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To understand what is electric current, it is very much important to understand what is atom and what is electron.
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So first we will learn about that and then we will learn about electric current with our simple train analogy.
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And this train example will make understanding of electric current very easy.
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So to get all of these details in the easiest way you need to watch the video.
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We have been listening right from our school that everything is made up of atoms.
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Our body, this ball, a wooden shit Everything that we see in our daily life is made up of small small atoms.
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As an electrical engineer, you may ask, why on earth I need to know about these atoms?
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But believe me, learning few basic things
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which I am going to tell you in next few minutes about atoms will help you to understand current
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and the materials from electrical perspective more easily.
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So moving on, every atom consists of three main parts i .e electrons, protons and neutrons.
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Thank you.
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Electrons has negative charge on them.
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Protons have positive charge on them and Neutron as the name suggests they are neutral
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which means they do not have any charge on them.
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In an atom, proton and neutrons are very tightly bounded together and this tight bounding is known as nucleus.
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As proton and neutron are very tightly bounded together, it is very difficult to add or remove any of the proton or neutron in an atom.
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Actually the total amount of proton in an atom decides its elemental identity.
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So if you can remove or add proton from an atom, you could actually change the type of metal.
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And by using this formula, you can convert any metal into gold.
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But we will leave that topic as that is not possible.
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Moving on, like proton it is also not possible to remove or add neutron in an atom.
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And adding or removing neutrons from an atom does not make any changes in its elemental identity.
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So don't try that too.
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However, electrons has freedom to move everywhere.
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They are like free birds, they can even go to another atom if pushed out and we can do that with very less energy.
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Electrons are like S -pole of a magnet and protons are like N -pole.
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As we know, two similar poles of a magnet repel each other but two different poles attract each other.
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and in similar way two particles with same charge will repel each other and particles with different charge will attract each other.
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To be more clear two electrons which are negatively charged will repel each other and in same way
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Two positively charged protons will repel each other.
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But, the interesting part is, like two different poles of magnet, two particles with different charge will attract each other.
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So negatively charged electrons are attracted towards the positively charged proton and vice versa.
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Now you may ask a question, if electrons and protons are attracted towards each other, then in an atom there would be always attraction and repulsion going on.
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The answer is no. To understand, look at this image carefully.
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The image shows the basic construction of an atom.
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Now, as you can see, there are four electrons and four protons are there in the above atom.
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So for understanding purpose we will consider charge on electrons equal to -4.
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as electrons are negatively charged and charge on proton are +4 as they are positively charged.
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So, to get the net charge we must add these two charges.
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So, +4 + -4 = 0.
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With this, we came to an important conclusion that equal amount of proton
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and electron in an atom cancel out the net charge and keeps the atom stable.
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Atom is stable only if the number of protons are equal to number of electrons.
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If I add or remove any electron from an atom, the atom will become unstable.
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and it is now ready to give or take the electrons to another unstable atom and become stable again.
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Let's say in our above atom I added one extra electron.
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Now the net charge is positive 4 plus negative 5.
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which is equal to -1.
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The net charge is not zero which means the atom is unstable.
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This atom will now try to lose one extra electron to another unstable atom and become stable again.
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We call such unstable atoms as charged atoms.
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Addition of electron in an atom makes it negatively charged and removal of electron from an atom makes it positively charged.
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The atom is like this train.
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In this condition the train is completely stable and not moving.
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But if we add batteries to it and turn on the switch the train becomes unstable and start moving.
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Now this train will keep on moving until the batteries gets dry completely or until we turn off the switch.
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Adding batteries to the train and turning on the switch is equivalent to adding an extra electron in an atom.
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As soon as we add battery and turn on the switch, the train starts and becomes unstable.
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And in similar way, as soon as we add extra electron in an atom, it becomes unstable and try to lose the required electron.
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Now let's learn about valence electron.
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Ladies and gentlemen, this is important to understand conductor, insulators and semiconductors.
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If you see this figure carefully, you will find that the atoms have different orbits which are shown by dotted lines.
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The electrons in the last orbit are known as valence electrons.
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The outermost orbit or also known as valence shell of an atom can have maximum 8 numbers of electrons.
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And, the number of electrons in outermost orbit of an atom decides the electrical property of the material.
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And hence, knowing this is important.
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If the atom has less than 4 electrons in its outermost orbit then the material can be used as a conductor.
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Examples are aluminium, copper etc. which has 3 and 1 electrons in their valence shell or the outermost orbit respectively.
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If the atom has more than 4 electrons in its outermost orbit, then the material can be used as an insulator.
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Nitrogen is one of the example of insulator which has 5 electrons in its outermost orbit.
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If the atom has exactly 4 electrons in its outermost orbit,
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then the material can be used as a semiconductor which has properties of both metal and nonmetal.
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Well if you know how many electrons are there in an outermost orbit of an atom,
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you also know if you can use that material as a conductor or as a insulator or maybe as a semiconductor.
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free electrons.
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The electrons in orbit near to the nucleus are tightly bounded to the nucleus.
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However, the electrons in the orbit
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which is away from the nucleus are loosely bounded with the nucleus as shown in the figure.
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We can relate this concept to the magnet and a pin.
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If the pin is near to the magnet it will experience more force
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and moving this pin away from the magnet will take some extra energy.
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But, if the pin is away from the magnet, the force will also be less
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and now we can move this pin with very less energy as compared to the previous case.
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In similar way, nucleus is like a magnet and electrons are like a pin.
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And therefore, electrons which are near to the nucleus will be tightly bounded and the electrons which are away from the nucleus,
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that is electrons in outermost orbit will be loosely bounded.
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And these loosely bounded electrons can be easily removed.
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We call such loosely bounded electrons as free electrons.
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if even if now you may think atom how many free free electrons are there
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but even if each atom gives one loosely bounded electrons we can get billions
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or maybe more of such free electrons from a Madal.
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good conductors of electricity.
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Material which has large number of free electrons are good conductors of electricity.
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Now if we make wire of such material and apply voltage across it, free electrons will start flowing from that material.
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And these are some good conductors of electricity.
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The best conductors of electricity are silver, copper, gold, aluminium in that order.
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It is important to know that not all the conductors of electricity provide same kind of conductivity.
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For example brass is also a conductor and silver is also a conductor.
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but the conductivity provided by silver is much greater than the conductivity provided by the brass.
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Since copper and aluminum is cheap and serve the purpose very well, it is used widely.
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In some cases silver plating is also done on a conductor to improve the conductivity.
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Now let's see the bad conductors of electricity or which is also called as insulators.
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Material which has very few or no free electrons are called as bad conductors of electricity or insulators.
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Even if you make wire of such material, no electricity will flow through it because it doesn't have any free electrons.
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Examples of insulators are like plastic,
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porcelain, glass, air etc. And But this insulator plays a very important role in many applications in electrical industry.
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For example, you can take cables which are present in our house.
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You can see that all the cables are insulated with plastic to avoid any direct contact with live conductor.
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And this insulator comes very handy saving so many lives every day.
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Now let's see about the semiconductors.
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There are few materials which has properties of both i .e conductor and insulator.
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At room temperature the material has very few free electrons and hence acts as an insulator.
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But if the temperature goes up to a certain limit, the material acts as a conductor.
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One example of semiconductor is silicon which is widely used in electronics devices.
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Yeah, so finally after learning the basics of atoms and electrons, it's time to learn about electric current.
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As we have seen, conductor which has free electrons can travel anywhere in the conductor if not directed.
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To understand what is electric current, let's get back to our train.
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This is our train and we want this train to go to the destination D.
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Well, if I start the train, train can go anywhere but not to the destination.
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But, if we place tracks from the initial position of the train to the destination D and turn on the train
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Now train will travel in the direction we want and it will reach to our destination D.
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Concept of electric current is not much different from this example.
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Tren represent the material filled with electrons.
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tracks is equivalent to the conductors and the batteries inside the trains is equivalent to the voltage source.
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The conductor has free electrons present in it.
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If these free electrons are not directed, it can move randomly in the conductor.
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But if we give them a direction and a path to flow, they flow in a coordinated fashion like our train travelled after placing the tracks.
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This directed flow of electron is what we call electric current.
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We can exactly relate this to our train example.
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The example makes the understanding of electric current much easier, isn't it?
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This uniform flow of electrons is what we call as electricity or electric current.
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Yes, it is as simple as that.
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You can consider a copper strip as shown in this figure.
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If we apply voltage to it, negatively charged free electron starts flowing towards the positive terminal.
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This directed flow of electron is what we call electric current.
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From this figure you can see
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that the direction of current is from negative terminal to positive terminal and which is correct as well.
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And this direction of current is called as actual direction of current.
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However, it was assumed that the current flowed from positive terminal to the negative terminal via conductors
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and this assumption is so firmly established that it is still in use.
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And this direction is what we call conventional direction of conductors current Of course,
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now we need a unit to measure the current flowing from a circuit or a closed network.
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Now, someone may say very large current is flowing through the circuit or very small current is flowing through the circuit but,
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How do we know if the flowing current is large or small?
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It is simple too.
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More electrons flows per second we can say current is large
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and when very few electron flows per second we can say current is small.
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The strength of electric current is electrons flowing per second, that is charge flowing per second.
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The unit of charge is coulomb which is represented by letter c.
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1 coulomb indicates charge on 625 multiplied by 10 to the power 16 electrons.
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My god that's huge isn't it.
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So 1 coulomb is equal to charge on 625 multiplied by 10 to the power 16 electrons.
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So the current
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The charge queue is measured in coulombs
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and the time is measured in seconds and hence the unit of current will be coulombs per second or ampere.
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If charge is equal to 1 coulomb
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and time is equal to 1 second then we can say that 1 ampere of current is flowing.
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If someone says current of 5A is flowing then it is basically 5 coulombs of charge flowing per second through the wire.
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And 5 coulombs indicates charge on 5 multiplied by 625 multiplied by 10 to the power 16 electrons.
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So if you want to increase the current flowing through a wire, you have to increase charge flowing per second.
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So, the unit of current is ampere or coulmbs per second.
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Ampere is most commonly used.
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Now let's see about the types of electric current.
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We can divide electric current in two main types.
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First is steady state current or direct current.
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When the magnitude
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or the amount of current does not changes with time as shown in the figure we call it steady state
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or direct current or in short DC.
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As you can see from figure current remains the same as the time changes.
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Current provided by batteries is direct current and it remains almost constant.
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The second type is alternating current.
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When current changes its magnitude and direction with time, then it is called as alternating current or AC in short.
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As you can see in this image, magnitude and direction of the current is changing with time.
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The current is flowing in alternate direction, half time it is in positive side and for the half time it is in negative side.
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And hence we call it alternating current.
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The current generated by generators in power station is alternating current or AC.
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So that was it for this video, in next video we will learn how we can make electrons to flow, we will learn about voltage.
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If you like the video do share it with your friends
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and do subscribe to my channel to get more such easy to understand videos.
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That's all for this video guys, I'll see you in my next one but till then,
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Keep watching, keep learning.
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Từ vựng và ghi chú luyện nói cho bài học này
Video này có 183 câu và 2520 từ để luyện shadowing. Phần lời nói dài 18:07. Người nói giữ tốc độ đều, khoảng 139 từ mỗi phút, vừa sức để nói đuổi theo. Chỉ 80% số từ nằm trong 3.000 từ tiếng Anh thông dụng nhất, nên từ vựng khá khó.
Từ vựng quan trọng trong video
15 từ đáng học trong video, kèm phiên âm và nghĩa:
| Từ | Phiên âm | Nghĩa |
|---|---|---|
| atom danh từ | /ˈætəm/ | nguyên tử |
| electron danh từ | /ɪˈlɛk.tɹɑn/ | ê-léc-trông, điện tử |
| orbit danh từ | /ˈɔɹ.bɪt/ | quỹ đạo |
| magnet danh từ | /ˈmæɡ.nɪt/ | nam châm |
| nucleus danh từ | /ˈnuː.kli.əs/ | hạt nhân |
| stable danh từ | /ˈsteɪ.bəl/ | chuồng, chuồng ngựa |
| terminal danh từ | /ˈtɚmɪnəl/ | nhà ga |
| pole danh từ | /pəʊl/ | cực |
| semiconductor danh từ | /ˌsɛmikənˈdʌktə/ | chất bán dẫn |
| wire danh từ | /ˈwaɪɚ/ | dây, dây thép |
| copper danh từ | /ˈkɒpə/ | đồng |
| destination danh từ | /dɛstɪˈneɪʃən/ | điểm đến, đích |
| voltage danh từ | /ˈvəʊltɪd͡ʒ/ | điện áp, hiệu điện thế |
| particle danh từ | /ˈpɑɹtək(ə)l/ | hạt |
| shell danh từ | /ʃɛl/ | vỏ |
Cụm động từ bạn sẽ nghe
| Từ | Nghĩa |
|---|---|
| turn off động từ | tắt |
Phát âm cần chú ý
Người nói dùng 5 dạng rút gọn, ví dụ isn't, doesn't, don't. Hãy nói theo dạng ngắn đúng như bạn nghe.
- Âm “sh” và “zh”: destination /dɛstɪˈneɪʃən/, shell /ʃɛl/, establish /ɪˈstæb.lɪʃ/, conclusion /kənˈkluːʒən/, conventional /kənˈvɛnʃənl̩/
- Từ dài — đặt trọng âm cho đúng: electricity /ɪˌlɛkˈtɹɪsɪti/, semiconductor /ˌsɛmikənˈdʌktə/, electrical /ɪˈlɛktɹɪkəl/, destination /dɛstɪˈneɪʃən/, positively /ˈpɑ.zɪ.tɪv.li/
Cách luyện với video này
- Nghe hết video một lần, chưa cần nói, và ghi lại những từ bạn chưa biết.
- Nói đuổi từng câu ở tốc độ bình thường, lặp lại mỗi câu đến khi nhịp của bạn khớp với người nói.
- Ghi âm giọng mình rồi so với bản gốc, chú ý các từ như atom, electron, orbit.
Ngữ pháp trong video
Những cấu trúc người nói dùng nhiều nhất, kèm đúng cụm từ trong video:
| Cấu trúc | Trong video |
|---|---|
| Câu bị động be + quá khứ phân từ — nhấn vào việc xảy ra, không phải người làm | is made · is known · are attracted |
| Mệnh đề quan hệ who / which + mệnh đề — thêm thông tin về người hoặc vật | electrons which are · zero which means · orbits which are |
Phương Pháp Shadowing Là Gì?
Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.