Electric Charge

by Patrick Ford
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Hey, guys. So I want to talk about something called electric charge. In this video, you're gonna need to know what for this chapter, but also for other chapters in this course. So let's get to it. But first off, I want to sort of briefly reintroduce you to atoms and atomic structure. So remember that atoms are made of protons, neutrons and electrons, and these protons and neutrons sit inside of this central structure in the atom that we call the nucleus. Whereas the electrons sort of float around on the outside and they orbit this nucleus. Now there's something special about these electrons and this protons. They have a property called electric charge, whereas the neutrons do not. The electric charge is a property of matter is just something that matter has similar to mass. So if you've seen the gravitation chapter, we can actually draw some important analogies between mass and electric charge. For instance, in gravitation, we needed mass in order to create a force and the mawr mass that we had the mortgage gravity or the stronger than that gravitational force. Waas. It's very similar for electric charge. You need charge in order to create an electric force and the mortuaries that you have the Mawr or stronger that electric force becomes now where things start to get a little bit different. Is that in mass and gravitation? We only assume that these numbers were positive. Positive. 5 kg 10 kg. Whatever. You couldn't have a negative mass. Well, physicist a couple of 100 years ago noticed that there was different interactions between charges such that there could be positive or negative. We'll talk about that a little bit later so you could actually have positive and negative charges. One of the other main differences is that in Mass, there was never like a smallest amount of mass that we could have at least physicists that seem to think so. But in electric charges, there is something called the elementary charge. What that means is the smallest amount of charge that something could possibly have. And it's a letter known as E, which is 1.6 times 10 to the minus 19 and the Capital C is the unit for that, which stands for cool OEMs. Now what I wanna do is I wanna make sure that you don't get confused between E and electron, so those were not the same exact thing. In fact, when we're talking about protons and electrons, we said they both have electric charge. Now the charge of a proton is going to be positive. E That's just something that we arbitrarily decided. We just decided to pick it that way. And the charge of an electron is going to be negative. E So this is just sort of like the magnitude and these air actually like these signs positive and negative. So whenever I'm referencing electrons in future videos, I'll try to do with capital letters and I'll write something like electron just so you don't get confused between that. Okay, so we've talked about protons and electrons having charge. So now objects that are not just those things. So Adams and things like that we see every day have charges well, and the net charge of any object is the quantity of imbalance between the number of protons and electrons inside of it. So I want to go ahead and draw a few examples. So we have an atom right here, and all you have to do is just count up the number of protons it has So you've got two protons over here, so that has plus two electric charge. We also have two electrons on the outside. So those two electrons contribute negative to E. So in other words, we have no imbalance between the protons and the electrons. So that means that the charges just zero. That's the net charge in this object. There's no imbalance, whereas over here I've got four protons inside of the nucleus. By the way, the neutrons are also in there somewhere. I just have drawn them and we've got plus four e from those elect from those protons and we've got three electrons on the outside. So that's three electrons, four grand total of minus three. Notice how these things are not equal. There is an imbalance. In fact, this one has one mawr proton. So that means that the total charge is equal to plus E. Now we've got four electrons over here and we've got two protons. So two protons for a total of plus two e, we've got four electrons for a total of minus four e. And so that means the grand total for the imbalance is that there are two more electrons than protons. So that means we're gonna have minus two e. Now, I also want to point out that neutrons neutrons have zero charge, so you don't never have to worry about neutrons or anything like that. Now I want what I also want you to recognize. Is that all three of these examples? These charges, the total number of charge was an entire multiple of E. There's a fancy $5 word you're gonna see for that called charge quantity, ization. And all that word means is that these things have to come into your multiples, e. You can't have half of a neat You can't have negative one quarter of any. It has to be negative one to, you know, 012 things like that. I have to be whole entire multiples and there's an equation they're gonna be using to calculate the total charge of something. It's something that we've used in all three of these examples. Just count the number of protons and the number of electrons. You subtract them and multiply it by the elementary charge. Now, sometimes in this equation, you'll see it in your textbook with ends instead, and all that end just means is the number. So sometimes you'll see it written like this N p minus e. But because it has e and e here, I don't want to say I don't want to confuse you guys, but that's something you definitely should be familiar with in case you see it in textbooks. Great. So most of the material that we're gonna see in physics are gonna be electrically neutral. So that means that the number of protons is perfectly equal to the number of electrons similar to how this example actually worked out. And so the total number of the total net charge of these objects is equal to zero. So you're gonna assume that objects are electrically neutral unless that problems specifically tells you that it's not. And that's it for this video. Guys, let's go ahead and take a look at some examples