Transcripts
1. Electric Charge: women teaching electric fields electric circuits. I often realise that my students manipulate the concept of electric charge without really understanding what it is yet on this turning the concept off electric charge is essential when studying any area related to electricity. This is why I feel important to dedicate a full class on the concept off charge. Prior to any course that deals with electricity, we will discuss what an electric charges. Actually, can you explain it easily? If not, you should take this class. After this, we we look at how we quantify military charge and also how electric charges behave in presence of each other. We will also discuss some of the most important characteristic off electric charges like, for example, the principle of conservation off charge and also the fact that when they move electric charges form an electric current, we will see that some materials allow electric currents to flow through them. And we will also see that some don't wise that find out by taking this class. By then you will have learned quite a few things. It will be time to play with some static electricity magic. I will show you how to move objects without touching them like a magician. And, of course, I will explain what is really going on after play back to work way, look at the definition of a charge in more detail by being introduced to the notion off electric fields. This video would just be a warming up. Yes, we will dive deeper in the concept of electric fields in the next class off this course, and finally, you will be able to test your knowledge with a series of questions and exercises in the last video. If you follow this class until the end, you will be ready to take on any other calls where electric charges are involved. So now.
2. What is a charge? (Electric Charge - Ep01): you might already have heard someone mention an electric charge like if it were not Recto, a particle of some kind. This is a common misuse of language. A charge is not. A definite body will object. It is the property often object. Let's tied into this idea. Take this pen. What can you tell about it? It's group, so I can say about the pen that its color is blue. That's what a pen, what else looks like? It's made of plastic. So the material of the pen Plastic. What else? No, it's heavy. No, it's not. Heavy is very light, but it still has a mess. 50 grand's more or less. What are these two columns? The one on the left is a property island light. It's a value off this property or the attributes. Let's call it value. Well, these are properties I could also like. Charge here. Charge is a property off the pen. Let's assume that is value is for now, zero. Now let's consider and really strong. And electoral is an elementary particle, which is part of an atom, an electron. It's also an object, said also has properties on values associated with it. For example, it's mass is 9.1 by 10 to the minus 31 kilograms. It also spends on itself, so it has a spin, which we can say it's a 1/2. It's just a value associated with the property. It also has a charge on the charge foreign. Any chunk is minus 1.6 by 10 to the minus 19. Cool, Cool. Oh, is the unit of charge. Let's take the pen there and what it onto a pull over. What happens here is that some electrons off the pull over a transfer to the pen. This is called the Tribal Electric Effect. So now let's suppose that one billion electrons went from the pull over to the pen. That means that the charge of the pen has increased by that off one billion electrons. One billion is tend to the nine that I need to apply by the charge off. One electron that is 1.6 by 10 to the minus 10. Cool. Now the pain will have a property charge off minus 1.6 10 minutes. 10
3. Quantifying a Charge (Electric Charge - Ep02): when we talk about the massive something we write down and equals above about kilograms. In the same way, when you talk about the charts off something we write down, two equals about cool. For example, the charge of an electron is minus 1.6 by 10 to the minus 19. Cool, 1.6 by tens of minus 19 is a special number for charge. It's called the Elementary Charge. What does elementary mean? Elementary mean that you cannot cut it into smaller bits. For example, if you consider an electron, it is called an elementary particle because you cannot cut it into smaller bits. But if you consider not home just made of a nucleus on electrons, allow them. That is not elementary because you can cut it into smaller bits. The electron and the necklace. Even the nucleus is not an elementary particle because it's made of nutrients and protons, so you can still cut it into small bits. Even the neutrons and the protons are not elementary because these also composed off quotes and blooms course are elementary because you cannot cut them into small pieces at least as far as our knowledge girls. Okay, back to charges so you can write the charge of the Munich shown as being minus e cool e stands for elementary the scientists that has shown the reality off this concept off elements charges called Millican in 1909 He designed an experiment to create many oil droplets in suspension and air. These droplets were off various sizes and he charged them. So the droplets got various charges on he was able to measure these charges. Say, for example, here 3.2 by 10 C minus 17. Follow here four points eight by 10 to the minus 12. Cool here that would be at the No. 7.2 by 10 to minus 30. Grow etcetera. What he noticed is that the charges are these droplets were all a multiple of one number This one the elementary charge. This is why you can write down the chart of something. Using the letter e. For example, take the helium nucleus angle. Nucleus is made off to nutrients and two protons. The charge of a proton is plus EQ. Therefore, the charge off a helium nucleus is plus two. Sometimes you write down even the charge on the symbol itself here to plus that means plus means plus e. So it means that the helium nuclear's has a charge off to e cool. When you wear the proton, you can write it like this and means plus e to the charge of the proton is one e cool saying for the initial you lighted e minus like this minus e cool. I need to exercise. Are you a new nuclear is made off 92 protons. It has also 143 neutrals. So the total number off neutrals plus boat owns is 235. Can you calculate the charge off this u n you, Nicolas, the chart off this u N you nucleus will be the some of the charges off its proton's so 92 times plus e in cool. So 92 by 1.6 by tens of minus 19 which is which gives me 1.47 by 10 to the minus 17 cooling which I wound up to 1.5 by 10 to the minus 17. Cool. Yes. In the data, I only have two significant figures Give my answer in 26
4. Conservation of Charge (Electric Charge - Ep03): you probably already heard about the law of conservation off Energy. It's also called the first Law of thermodynamics. If you consider a system which is closed, meaning that you cannot put energy in and energy out, the energy inside the system will always remain the same. It might change form. It might go from one form to another within the system, but the total amount will always stay to say it will remain constant. You can say the same thing when it comes to charges. If I had an isolated system with a certain amount of Charles Que in it and I cannot charges in a lot, this charge will stay to say it cannot be created or destroyed. Let's take an example. Imagine a photo. What is the photon? A photo is a particle of light, but it is also a certain amount of energy which is moving around, and I can imagine another one and they meet here, said means if these photons have got a lot of energy that at this point I have a huge amount of energy when you have a lot of energy in one point, this energy transforms into mass, you know equals, and he squared well. For example, we could imagine these two photos transforming their energy into an electron, so they made a nature on from the energy. If nature made things happen that way, it will violate the principle consolation of charge. It doesn't happen that way. What happened is at the same time, in literalness formed there is the same particle, but with a positive charge, which is formed at positron. If you look at the charts before and after the final minute before where photos have no charge, so Q equals zero and after I would have minus E and cool plus E in cool. Giving me zero charge is conserved. Let's go to do an example in chemistry. Now imagine that I have a glass of water and inside the glass of water, I want to put some table salt sodium chloride. That's my Donnelly action. Sodium chloride, as solid will become so doing dissolved plus growing this old. But when you do this, the soldier on gays in a trance is applied, so you have plus here and might instead and you see that the charts before is equal to the charge after because he got plus e on the minus eat, which is you. Another example. Suppose I want to put some sulfuric acid a true and so forth. So he h two s 04 I would give you two hydrogen and once who fate and once through faith, the Hydra germs are ionized here. So they each have given away one electron on the sulfate. I am has to extraction, Tony. So you see that the charges also conserved que here zero plus two e miles to eat This principle of conservation of charges always true. What is the situation when he has a system which is close, We need, you know, putting charges in a while artificially. The charges that you have before reaction will always be caused to the charge that you have at the end. When our universe was born, it started with a certain amount of charge. It will die with the same amount of jumped
5. Electric charges attract and repel (Electric Charge - Ep04): consider two particles. They both came. Your charge on the sign off. This charge is positive. You already probably know this, but thes two particles will feel repulsive force because a sign off their charges, respectively, off the same nature, they both positive they've these particles can recharge it, which were both negative. Same story. So charges off the same sign repair. On the other hand, if the two particles had charges of opposite side, there would attract each other well, the force of attraction or repulsion between two charges. It's called the Coolum Force. Cooling force is proportional to the product of the two charges and inversely proportional to the square of the distance between them. That would be here so naturally there with a convention that comes up about the sign of the force. You see, if the two charges have opposite science, F becomes negative. So when f is negative, it's an attractive force. If the charges have got the same sign we were applying negative, negative or positive, I positive you get a positive value. So when the forces of repulsive force it's positive I would talk about the Coolum force more in detail in the next class. For now, let's have a little gray and then it's a bit of fun with what we've learned up to now I have a weather balloon here and there. Have a PVC What? Let's bring the PVC world close to the blue. Not much happens as you can see. Now I will Web balloon with my full over. When I'm doing this, I'm transferring electrons from my pull over to the blue. So now the balloon is negatively charged. I could hold it with the hand because a balloon is insulating when charges arrival miss a spot, they stay there. That's the same thing with the what? Here I'm also negatively charging the world. Let's see what happens when I bring the world close to the blue repulsion. The reason for this is that the world is negatively charged as well as a blue. So when you push him from each other
6. Electric Currents (Electric Charge - Ep05): if I tell you electric count, what do you think? Well, you probably think about a wire with some electrons moving in the way. Flow of electrons on electric count is not necessarily a floor village. An electric current is a flow of charges. So if you have electrons in a why which are moving? Yes, you haven't any should count because you have the child is carried by. The electrons are moving. Actually, you just need to worry. Electron right? One Electra moving even if it's no in a why. Whatever. Wherever it is, we create a current because it's a flow of a charge. If I take a soldier iron, which is moving that also will generate a current because he's a charge is moving. Let's go back to the wire. Imagine. I have a wire here and I put lots of positive charges there which are fixed. I blocked them and here put some electrons where what will happen? These electrodes will be attracted to the positive charges. They can move well, so you have flow of electrons. Therefore, a flow of charges therefore account. I can also imagine some water and in the water have some sort. Therefore I've got to sodium plus irons on Khloe and minus items. Suppose it in the water in place of bar and here put lots of positive charges. When the chloride ions are going to see this, there will be room attracted to it. So there we floatable, two positively charged bar. They can be a charge. Therefore there will be a flow of charge. There's also is a military count. What I wanted to make here is that an electric town is not necessarily a flow of electrons . And then it recount is a flow of charges in a wire here that these charges happen to be carried violent drunks. Therefore, sometimes people made the confusion the child carries can also be other things. I'd like irons, and when they move they also generate an electric current because when they move, the charges moves with
7. Electrical Insulators and Conductors (Electric Charge - Ep06): the ability of a material to allow charges to move within. It is called its conductivity, but a charge is carried by a charge carrier, a particle, usually the electoral. So the ability of the material to have a direct current within it depends on the ability off the charts carrier to move around. Let's consider material as a resentful mm diamond. Do you know what diamond is? NATO Diamond is made of carbon atoms, which are arranged this to the way the carbon atom contains an inclusive Mitchell's and four of its electrons are dedicated to be shared with something else. These are cold valence electrons, so in a diamond, all these electrons are shared with neighbouring carbon atoms to make bonds. So imagine a put a positive charge here. Sure, these electrons will feel the force would be attractive, but they can't move because they are used to make the bond between carbon atoms. Therefore, here you cannot have a flow of electrons. You cannot have an electric count within the diamond. The diamond is called an insulator. It doesn't allow electric counter for food. I just want to do another full of carbon left fight. Girlfriend had got a different structure than diamond. Carbon atoms only share three electrons with their neighbors, leaving one dangling around. I've just presented carbon left from here. I leave that to bonds. Each ball is made of two trumps. You see, This one is free. So if I put a positive charge there, this one will retract it. I will be able to move. I can imagine other carbon atoms off graphite here and this one goes away. Replace maybe this one and then this one by this one, etcetera. So you have a flow of electrons and therefore you have a friend of the charges they carry. You have a military count. Graphite allows electric counterparts suit. It's called a conductor. Another type of good electric conductor are metals. What does the metal? Well, a metal is made off at times a little obviously like, for example, a couple. But these do not form individual bonds like this. Instead, they share the electrons to the whole system to the whole community. So you have copper two plus here and to drones, copper two plus. And to Lake Charles and cooperative class and two electrons. Andi intellectuals form like a cloud like glue holding the whole thing together. So you see the link between the atoms and each one has a week. So if I put a positive charge here, the patrols would be attracted. They will move therefore, because they move the charges, moves with them. You have an electric car to settle eyes. A conductor is a material that retains charge carriers, which are free to move around. All the other hand and into later is a material where the charge carriers are stuck. They cannot move freely. As a consequence, you can have an electric current in a conductor, but it is very difficult to have an electric current in an incinerator.
8. Electrostatic Games Part 1 (Electric Charge - Ep07) : This is an aluminum camp. This is a plastic what plastic is PVC on. This is a full, over made of wood. It's pretty need. Don't you think it looks like magic? It's physics. You see. All matter is made of three particles. Drunks, protons and electrons. Neutrons, as they named suggest, are electrically neutral. Photons carry a positive charge, and electrons carry a negative judge. How are these particles organized? As at homes we got in an atom and nuclear, I would contains neutrons and protons on a louder nuclei. You have any jewels, the number of electrons and number protons. It's the same in the natto. Therefore, the church off the atom. Yes, even Tom's are neutral. These are Tom's organize themselves as molecules. For example, the water molecule, one hydrogen, one oxygen and the hydrogen Thea Thomas being neutral molecules are also neutral. Let's look now at a block of matter. Come trains atom's molecules. Therefore, some nutrients from protons and some electrons. The block of matter will be neutral because the monitors and the atoms are neutral. So the whole broke his neutral. This book can be anything and can be Ah, this board. It could be the span. It could be my finger. Whatever. We can consider another block. It will also be made off neutrons, electrons and protons. But these in this block will be organized differently. You have different atoms. If in molecules therefore different properties for the material, for example, this block would have other property. The fact that it can take some extra electrons, it actually enjoys taking extract. Jones while this broke would be move kind off. I want to get rid of some. So if you place them in contact and love them against each other family. Charles, my transfer. This is called a tribal electric effect. And now, if you separate them after having web them together, the red material will have an extra amount of Eric Trump's, so it will be negatively charged while this one will have a default off electrons. Therefore, there'll be more protons and Eric Chance, so it will be positively charged. Consider these two materials, so pull over would be the blue thing on the Web thing would be the PVC world. And when I web them together for this on actually transferring some electrons from the polota to the world, this is a status off work now it has a negative charges accumulated at the extremity that I wept again to pull over. PVC is an electrical insulator. That means electrons cannot move around. BBC they are kind of stuck there. So, for example, if I took an H on hereby webbing the pull over at this point the electron allied there, then the electron is stuck there. Therefore, the charges here are localized. At this point, they cannot move. Let's look now at the aluminum can. I would presented it here, seen from the bottom So you can see actually a cylinder of aluminum. Aluminum is a metal and the metal is an electric conductor. That means that electrons can move around the metallic cylinder and metal is also like any other material neutral electrically. Therefore, they are as many protons than they are electrons. There are as many positive charges that they are negative. Charges second represent the positive charges on as many negative charges which are dispersed uniformly inside the material. Suppose that I approach and then getting Lee child book directions can move around a mental . Therefore they will move around with payrolls by these negative charges there will move away. So the positive charges they can't move because of positive charges are carried by the nuclei off the atoms that form the structure of the material. But still, you would have an accumulation of negative charges this way, and you will have a default off negative charges. That way, That corresponds to a positive charge. India second will move this and just plays by big minus Here on the big plus there, the aluminum can has become an electric die Po. Okay, so we have our world there on. We have the negative charges there they get even negative, repel each other. So that will be repulsive force like this. But you also know that negative and positive charges attract each other their full There will be at attractive force like this. There are two forces going on, one attractive one repulsive. These forces are called Coolum forces and it could be written like this when you have two charges Q one and Q two at a distance d from each other force between them is proportional case constant to the product off the two charges and inversely proportional to the square of the distance between them. Don't be frightened by the formula. What's important here is and the fools if the inversely proportional to the square of the distance, meaning that further away the two charges smaller the force. So you realize that the attractive force will be stronger than the repulsive one because of positive charges are closer to the world, then the negative ones. And that's why the can will follow the world. You might argue that the cat is not moving like this. Actually rolling. That's not a problem, because remember that the electrons can move in the metal. Therefore, they'll try to find the point, which is further away from the negatively charged what and there'll be willing to so that this configuration always stays the same when the world alone.
9. Electrostatic Games Part 2 (Electric Charge - Ep08) : Oh, a plate. Some water bubble soap, PVC would on my Panova. Look at the magic. I'm controlling the bubble. I'm most of the bubble. I can even change the shape of the bubble, but I need to be careful not to pop it. We saw that the soap bubble was following the negatively charged rod like the candles. What is this So bubble, anyway? I represented one here. This is a layer of water and that the interface between the air and the water. There's another earlier cord, a surfactant lee. It's a silk basic. What we interested here will be actually the water later, because it's not pure water Here. It's just tap water in tap water. That's, um impurities. His impurities are charged. Think about that, tops, Right? I told you that at times for neutral. But if you will move an electron at the nature into these atoms, they become charge. There no atoms anymore. They become irons. Take the soldier at all. If I take away an electron from the soldier madam, there will be one extra port on, compared to the number of electrons. Therefore, it would be positively charged. Take the clothes line at home. If I add one any trying to the kloten at home, there will be one extra electoral. Therefore one extra negative charge. It will be negatively chance. These are irons on tap. Water is full of them. Irons can move in water as they want, like electrons in the metal. So if I approach and they get, if you're charged, bar him the sodium irons. I come to want to move closer to the bar because they're positively charged and the climbing irons we want to move away. Do you recognize the situation? It's like with the can. Here you would have an attractive force between the negatives and the positives and here repulsive force between the negatives. But because the positive charges are closer to the negative ones off the power, attractive fools will be bigger than the repulsive one. Therefore, as a hold, the bubble will follow them. Getting a job. What
10. Full Definition of an Electric Charge (Electric Charge - Ep09): In the first video off this class, we learned that an electric charge was a property of a body, or the system in science at property describes a characteristic of the body exposed to certain conditions or stimuli. The chart of a body defines how strongly its motion is affected by an electric field. We will study in depth the notion of electric field in the next gas. In a few words, An electric field is a region of space where charged body experiences a force. Let's imagine that this board is an electric field. Let's also imagine that the field is uniform, meaning that it is identical in all points we define how strong you feel is by the letter. He means electric field strength on a trip feel has a direction. Therefore, the electric field strength is actually a vector, and the magnitude of the doctor tells you how strong the feel is. At that point, right? If I consider this point, I would have in any field e like this. For example, I told you the feelings uniforms, saying I don't think we know points. If I take another point here, I have the same you to feel strength. And now here, the same Olympic field strengths, etcetera. Okay, Now I will place in this field a body which is carrying charge. Little cute because I'm placing it in an electric field and it has a charge. This body will feel a force. This force will depend on how strong is a field, right? And it will also depend on the magnitude off the charge. You see, the force experienced by the body will be proportional to the strength of the field on also to the charge carried by the body. So it will impact the motion off the body. The charge will impact the motion of the body in a nature field. That's what charges I could even developed a bit further. Imagine that this force is the only force that his experience to buy the body. That means that this force is also the net force. The net force of my body is just a some of the forces on that body. If this is the only one well and that force will also be equal to E that Newton told us that the net force on the body is equal to M a mass by the acceleration. That's a second loan. Neutral. So could we wrench this and like a a subject? What does this mean? The electric field strength is constant. We said it was uniforms. The mass, obviously of the object one changed. It is also constant. That means that here the acceleration is proportional to the charge. What is acceleration? Acceleration is rate of change of velocity. So tell me how motion changes, how fast it changes. And it's directly proportional to cute. That is nearing right in the definition of what the charges. The charge of the body defines how the motion of that body will change when you place that body in an electric field. This video concludes this class dedicated to the electric charge. I hope that now we have a good understanding off what an electric charges and I invite you to check your knowledge in the next video which contains a quiz. I also recommend that you continue this course. Yes. In the next classes, I will discuss the cooling force between two charges. Electric feels electric potential and electric currents and all of this. We lead us in the end to learn about electric circuits and how to manage them. So see you soon
11. The Quiz (Electric Charge - Ep10) : I thought your nucleus is made off 11 protons and 12 neutral. So in total, you have 23 nuclear wings within the nucleus of the sodium atom and Nick Leone is either a neutron report. Okay, so what is the charge off the soldier necklace? Well, it will be the charges of its photo there. 11 protons. So it's going to be 11 times the charge of the proton. Have a child of the proton is one service 11. So in colon we get 11 by 1.6 by 10 to the minus 19. Excuse me. 11 by 1.6 10 months. 19 Want with 76 by 10 to the minus 18 Groom, That is if I wound up 1.8 5 10 to the minus 18. Cool way. Have a proton of charge Que of the proton is equal to e. And here we had a hated Nicholas which had a charge killed the healing knickers too. I place an electron in the middle. Well, this electronically feel to force is right. It will feel a force of attraction. Due to this Bo Tong, I'm a force of attraction Due to this helium which one wins. Well, remember that the force between the two is expressed like this Q one, Q two over these quit the distance between the electron on point A and point B is the same because he trump is in the middle. So that will not count here. What could be the charge of the election? And you too could be the charge off either The proton, those a helium. I really realized that the charge of the helium is bigger and that of the proton. Therefore, the force due to the helium will be stronger. So if you saw the two forces, the literally had a net force diet tip to with him, so the literal will go towards the heat. If I were a plastic world on the cloth, the plastic world will take electrons away from the cloth so the plastic water will become negatively charged. Imagina tastic would like this and I wept this section. Therefore it got negative charges. If I would be this with another world, well, there'll be negative charges to at the place where worked what they save Paris negative. So these two worlds, at the size of the world we repel each other. I could imagine pinning them around an axis here. Value. What has it wants to likeness? Oh, way have to Metallica balls. The 1st 1 is neutral and is a temperature. What? So it cannot move about? The 2nd 1 is negatively charged on is attached to a string so it can move about. Now you know that metals are conducting materials and in conductors, electrons can move around. So in the neutral, the electrons are going to try to go away from this book repairs by the negative charges. Therefore, there will be a default of electrons here, therefore positive charges. So now you can guess what will happen. This ball is going to be attracted to that one because it *** the charges it holds attracted to the positive charges on the side of this boat. Now imagine that, um, this ball touches that one. You would have a contact here on. This can be seen like one single body because it's a metal. The electrons can move around the metal. So some of the rituals I get to go there and they can distribute themselves in order to pat himself have maximum, right? They're full some of the chart of the scoreboard. Some of the negative charges a small book is going to end up in the bay One. Now you have two bulls that can negatively charged. Therefore, this ball will be repaired by that one, and we lose contact.
Edouard RENY, Music Producer & Tutor in Physics
