okay, gang. we know that matter is made of atoms, and the atoms are made of what? the atoms have a central nucleus, say positive. and around that nucleus orbit, say, a little particle called an electron, and this carries the negative part of the charge.

it's this little electron that carries the negative charge that makes up electric currents in wires--electron. it turns out this and this, these charges are opposite and which belies a fundamental rule of electricity. opposite charges... attract. --attract. and like charges... repel. repel. repel. that's right. and so the negative charge is being attracted to the positive charge and whirls around, around, around in a very loose sense, in almost an incorrect sense. but we can think of it like a sun here and a planet going around and around and around. the force that holds the planet to the sun is the force that we don't understand it very well. we have a name for it begins with g. what is it? gravity. gravity. and the force that holds the electron to the proton is the force we call... electricity. begins with the e. -- ends with a l. electrical. electrical. it's the electrical force. so there's an electrical force between these two. now, we normally say that that atom has no net charge.

do you hear me when i say no net charge? there is much positive as negative. in fact, if i had another charge, like a charge over here, a negative, this negative charge over here wouldn't even see that. it wouldn't sense it. it wouldn't sense a thing 'cause this negative charge is what? being attracted to the positive, but is being repelled by the negative, and the distances are about the same, so it turns out it's a wash. so a charge over here doesn't notice electrically this atom over here. so the atom is neutral. so we have a neutral atom. but let's suppose this charge is closer, like over here, and let's suppose its part of another atom, like another hydrogen atom. oh, this charge here now is closer to the proton than it is to the electron. so there's an attraction to the proton, a repulsion over here, which is not quite as big. it's a little further away. so we have now a net attraction.

and do you know what happens to this atom here? it... [makes noise] it clumps together and it becomes a molecule. when you study chemistry, you'll study about the different bonding forces. and all those bonding forces that you study, are guess what? begin with the e. electrical. electrical. they're all electrical. you are held together by electrical forces. electrical forces comprised all the bondings that you have in chemistry. it's simply electrical forces. and these forces behave in a way very similar to the way that gravitational forces behaved. remember we talked about the force of gravity? and we said the force of gravity, there was a force in the universe that was proportional to the mass of one object, the mass of another object, divided by the distance square. remember we talked about that? well, physics is neat, gang, because guess what? it turns out there is a force that's very much the same between electrical charges, and that force depends upon

the quantity of charge on one object, the quantity of charge on the other object and depends on the distance square. isn't that neat? whip, whip, same, same, which is one of the nice things about physics. things that seem so diverse really have a commonality. and so this is called coulomb's law. coulomb's named after a man about 150 years ago by the name of james j... >> law. >> law. right on. okay. and newton's law of gravity is named after a dude named... gravity. gravity. okay. we got that. we got that, okay. but we have these two things here. and all the coulomb's laws said is, "hey, the force of attraction are repel, oh, one difference, electrical forces can attract or repel." oh, so you can shield out electrical forces. gravitational forces only attract. there's no way to shield them out, but you can shield electrical forces. but it just simply says, "the amount of attraction or repulsion "depends upon how much charge you're talking about and how far away the charges."

if they're very, very far away, then the force will be very, very weak. if they're close, close, close, the force will be strong. just exactly what you would expect. the same thing you'd expect with planets in the universe. planets far--very, very massive, more force of gravity, close together, more force of gravity. same type thing with electrical forces. any questions at this point? wouldn't a minus be part of the constant or proportionality for the electrical force? class, i haven't even talked about constant and proportionality, but it-- do you know what lee was talking about when he talks about the constant or proportionality, gang? no. remember the constant or proportionality for force of gravity? if you took the force and divided it by this, you'd always get the same number, and that was that big g, 6.67 times 10 to the minus 11, okay. that was the constant or proportionality. over here, if you take the force between a couple of charge particles and divide that force by the charges and the distance between, you will get the same darn ratio no matter what set up you talk about.

and that's the constant of proportionality and we call it k. over here we call the constant g. now we don't talk about a proportion, we talk about an exact equation where g and k make this side and this side, newton's, newton's, same, same. other questions? yeah. from the center of an atom, you have more than one proton, which are two positive charged. yeah. this is for a hydrogen atom, now. yes. let's supposed i have a helium atom. now, we got two protons. it turns out there's two neutrons here too. and you know what? you know what's gonna happen to this space over here? take one guess. everyone. everyone. this charge out here now sees two protons tugging on it. how many say, "it'll be pulled into a tighter orbit"? how many say, "no, no, no, it'll stay the same"? how many say, "no, it'll be pushed further away"? check your neighbor. -- how many say it's gonna be tighter? yay, that's right.

and it turns out, for a helium atom, the helium will hold the electron tight. and furthermore, it will hold another one too. the fact it holds another one makes it a little bit bigger, okay, 'cause they're repelling over here. but a helium atom is smaller. it turns out a helium atom won't gang up with any other atom, so there's no such thing as a helium molecule. we have two positive charges right next to each other like that, how do you deal with that? why don't those two positive charges repel? why don't they repel? look how close they are. they're right up against one another? why don't they repel? and let me say this, the electrical force is awesome. it's a billion, billion, billion, billion times stronger than the gravitational forces between these particles. billion, billion, billion, billion. so it's an enormous electrical force tending to repel them. and why don't they simply repel? well, it turns out you're gotta get to the last chapter in the book. and the last chapter in the book you find out,

honey, there's a force even stronger than the electrical force, yes, there is, but only up-close. and that force is called strong force or weak force? strong. strong force. call it strong nuclear force. and it's a strong nuclear force that holds this thing together in spite of the electrical repulsion. and later on, you're gonna learn that when a nucleus gets too big, and these charges are far away, the nuclear force holding them together is weak compared to the electrical force, so they fly apart. and we'll learn that those atoms are called radioactive atoms. and all that has to do with the electrical forces between the nucleons. so this is another force that we haven't talked about that overwhelms the electrical. any other questions at this point? let's talk about charging. here's a piece of cat's fur. it's for science. and here's a rubber rod. what i'm gonna do is i'm gonna rub the rubber rod

against the cat's fur. now, what i'm doing... [meowing] [laughter] [meowing] [laughter] i don't know what that is. but anyway, what i'm doing here, gang, is what? i'm rubbing electrons from here on here. and you know why? it turns out every substance-- it's holding its electrons, yeah? how many say, "oh, all substances must hold their electrons with just the same force"? coincidence of coincidences. no way. that's not true. different things will hold electrons with more force than others. and guess what doesn't hold electrons very good? it begins with f, ends with r. i got a u in the middle, try it. fur. fur. or your hair. okay. guess what holds electrons very nicely? it begins with r, ends with u-b-b-e-r. rubber. rubber, okay? and so when i take the rubber and i scrape it against the fur, what am i doing? i rub electrons from the fur onto the rod. now, the rod has more electrons than before. you, people at front row, can you see those things?

yes. okay. [makes noise] follow me, i'll make your crops grow. hey--okay. it turns out-- no, i'm kidding around. but there are more electrons on here than before. so i say this is charged. now, you got to tell me, negatively charged, or positively charged? negative. neighbor. how many say negatively charged? all right. that's because the electrons themselves are negative. and by the way, do you know who is the one who put-- who gave us the idea of negative and positive charges? a first, first-rate scientist with a world-wide reputation in science. his name was bf. benjamin franklin. benjamin franklin. that's right. benjamin franklin was noted as a first-rate scientist before he became a statesman for 13 the colonies. benjamin franklin did a lot of work in electricity. benjamin franklin is said to be the isaac newton of electricity, an enormously prominent scientist in his day before the 13 colony-type thing

and before signing the declaration of independence. ben franklin, he did a lot in electrostatics. so this then is negatively charged and the cat's fur then would be? positive. positive. which, by the way, underlies a very important principle called the conservation of charge. and the conservation of charge simply says that, "hey, gang, whatever charge you got, "it's what you got. "you don't make any more, you don't make any less. all you do is transfer it from one place to another." it's like maybe a brick road. there's so many bricks in the road. now, you take some of the bricks off the road and put them on the sidewalk. what's the total number of bricks i have before and after? same. the same. i've just put them from one place to another. and every brick in the sidewalk is matched by a hole in the road. do you see that? so we just take it from place and put another. so if i put a certain charge on here-- let's say a millionth of a coulomb-- coulomb is a unit of charge. if i put a millionth of a coulomb on here, and that's negative, what's the positive charge?

a millionth of a coulomb positive. can you see that? it's just kinda make sense, okay? let me get a-- it's a ping-pong ball painted with a metallic paint. it's a conductor. now, what i'm gonna do, i'm gonna charge this rod up. i'm gonna put some charge on here, onto the ball. and i think you can see that. when i get the ball charged up. watch this now. repulsion. did you see that? so like charges do what? repel. now, let's suppose i take this glass rod and i rubbed this against a piece of silk. now, this is gonna become what? positive or negative? negative. how many say, "oh, i don't know." this can be positive. and we can find out if it's positive by doing what? bring it over here, and sure enough--you see that? opposite charges attract. isn't that neat?

here's a nice little thing here. let's suppose i take this down and put a non-conductor up there, like this piece of popcorn from packing material, huh? let's try this. okay. now, that has no charge at all, okay? if it does, it would ground off to me. i would ground the charge. but it's non-charged. watch this. even though it's non-charged-- see that attraction? it attract it or attract it then repelled. why is that true, gang? it's attraction, attraction, attraction and pretty soon i get enough charge on there so-- but you see there's an initial attraction. let me try that with a charge of opposite sign. here's a positive charge. and it still attracts.

why? why that's true is very interesting. it has to do with the-- an idea called charge polarization. let me show you what i mean. in this little piece of material here are little charges. they're just as many positives as negatives. when i bring the rod over-- let's suppose the rod is negative. the negative does what? pushes the negative part of those molecules over to one side and pulls the positive side-- positive end this way. for example, i have a little molecule like that, it will probably go like that. tend to pull it like this. now, the charges are moving through the material because it's an insulator. but the molecules in there, i can reorient and pull the positive side toward and what do we got now? now, i got the positives and negatives. what are like-- unlike charges do, gang? attract. attract and sure enough we saw an attraction. but that would work as well if i have the glass rod, as you saw. if i have the glass rod here and i have positive charge, now, what do i do?

i take these molecules and flip them the other way. this is what happens. that's why you can take, like, a little piece of paper. here's a little piece of paper here, okay? it has no charge. but i can charge up, say, the rubber rod and i'll find out that the little piece of paper attracts. you see that? what i'm doing is i'm polarizing the charge distribution in the paper. and that's what i'm doing over here, too. i'm polarizing it. and so now, i have my little molecules like this. the negative is pulled toward, the positive farther away. and since the positive is farther away, there is what? there is a less repulsion and more attraction because this is closer. closeness wins. and so what happens, the whole device comes over. i can show you charge polarization in another way. i can show you that with this. here, we have a piece of plastic. this piece of plastic holds electrons very readily.

i can just beat some electrons on here, and i do that. [laughter] now that's negatively charge, huh? now, i take this piece of conductor. it's a piece of pie pan, huh? and it's metal. metal's a good conductor, easy for electrons to flow through, right? especially if there's a little electric pressure. and guess what we're gonna talk later, electric pressure. anyone who know a name of electric pressure? begin with a v, end with oltage. voltage. voltage, very good. okay, we're on to this stuff. not so bad, yeah. but notice i have a wooden handle. why the wooden handle? it's a good insulator. electrons won't flow very readily through a wooden handle. if i put this down on top of there, should this be charged? i turn it over and it isn't. but what happens when i touch it with my finger? see that, see that, see the difference? isn't that neat? okay.

so we find it's charged when i touched it with my finger. let's take a look at this in more detail. here's my piece of plastic material and i beat a negative charge on there, yeah. and i took the pie pan and i put the pie pan on there like that, okay? now, what happens in that pie pan? any free charges in that pie pan? yeah. any charges in that pie pan? show me the piece of material with no charges. no way. there's charges in everything. there's atoms in the pie pan. and aren't the electrons loose in all metals? isn't that true? so the electrons are gonna be repelled by the electrical-- by the negative plastic. so the electrons are gonna be pushed to the top. and what's gonna be pulled down, gang? begin with a p. positive. the positive, see. i'm being careful to draw as many positives as negatives. why? because there is no net charge, and we saw that.

if there are net charge now, it will flow off through my body. okay. but now, there is none and there's still none. no net charge. but what happens when i put my finger there. what happens then, gang? when i put my finger here--okay? when i touch it with my finger, then i afford a what? why does it become charged? and let me ask you question. when i do put my finger there, you saw it becomes charged, why? and what kind of charge? check your neighbors. hey, gang, i can show you that it's charged by lighting up this little lamp. let me get this away now, no charge. by touching like this, boom, no light. no light, no light. all right? now, let me touch it. light.

do you see that flash of light? can you see that? let me try it again. let me try it in the dark. just watch. now we saw it. that was nice. can you be seeing? yeah. yes, i can see it now. all right. thank you. so you guys thought i was putting you on, right? all right. all right. yey. you could light up cities like that if you had someone keep doing that, right? yeah. we have a better way. i'll show you next week, okay? let's look at this device here. it turns out how much charge can be stored on those little-- there has to do with the radius of curvature of the ball on the top, yeah. the radius of curvature. what would happen if we have a large radius of curvature? store a lot of charge or a little? -- right here, gang, we're gonna be seeing this, yeah. but how about if you have a small radius of curvature like this point? it's a very, very sharp point. very small radius of curvature.

will that store a lot of charge or a little? answer begins with a l? little. a little. in fact so little, it won't-- watch this. when i touched the point this time, and i come over like this, i guarantee you, you will not hear any lightning. crank this thing all night long and--no way. you know why no way? because that point is so sharp that charge capacity there is so small that any charge that gets on there leaks off as fast as it gets on. so the charge leaks off and here you see there was a prevented-- that we prevented lightning from happening and guess what these points are useful for, gang? lightning. on your barns and on your homes, lightning rods. that's right. let's look at lightning a little bit, okay?

here's the ground down below. here comes a cloud. maybe the cloud is all negative on the bottom. if it's negative on the bottom, guess what it is at the top, gang? positive. positive. that's right. and that cloud is gonna induce a charge down below here on the ground. it's gonna induce a charge. it's sort of like this cloud coming overhead and here's the ground, down below, yeah? and the cloud comes overhead and induces a charge down here. and what it's gonna do is it's gonna drive electrons down unto the ground and it's gonna pull in effect, what up? plus. now, we have an interesting condition, gang. we have negative charge here. we have positive charge here. we have opposite charges like we had here with no lightning rod. what happens if the charge build up-- what happens finally? a ba-boom. huh? and what happens when a lightning cloud

comes overhead and it can't quite make it? you know why? that gap is too big. and you're out there playing golf. you're playing golf with you're friends, huh? and you're out there and you take your copper shoes with the little cleats and you stick them into the soggy ground, right? you're friends says, "hey, we better get out of here, there's thunder clouds coming over." he say, "oh, just one last time." [laughs] really one last time. you take the copper rod, okay, that copper club and you lift it up in the air and here you are right here, okay, and you lift that club right up in the air, what does the cloud say? the cloud says, "santa claus has come to town. i think i'm gonna be making a little visit," right? because now the path is short enough and-- and then you get it. many people get wiped out every year on golf courses because they find themselves the closest part to the cloud. and the closest part, nature's a little bit efficient or lazy, however you wanna put it and-- they get wiped out. even that happens at homes too. if you have homes here, buildings.

do you see the buildings are closer to the clouds than the ground down below, okay? now, this really perplexed people in the old days. because in the old days, the tallest building in any community was-- you guys know what it was? church. the church. you see? and it was always-- it was thought that lightning was the wrath of god. lightning was god's way of getting angry and a little bit upset, yeah? now, what's the last building in town that should be hit by lightning, gang? the last one especially if no one wears lipstick and won't play cards and everyone is properly guilty for any pleasure they have, okay? and what building should not be hit? -- but guess what building, time after time, no matter how little lipstick, no matter how much tithing, no matter how devoteful, no matter how much praying, guess what buildings were all the time getting belted by lightning? begin with a ch. church. figure that one out. that had a lot of people perplexed. benjamin franklin was a unitarian. and in philadelphia, benjamin franklin discovered

these ideas we're talking about now and he put the first lightning rod on the unitarian-- now, you knew-- you know who the unitarians are? they can play cards on saturday night. they can even drink liquor, okay? they can wear all the lipstick they want. they're thinking about the cosmos goes beyond those little concerns, right? but people thought that if any building gotta get hit, honey, it ought to be the-- and guess what? never, the unitarian church didn't get belted. and one by one the churches started to put lightning rods 'cause what's the primary purpose of a lightning rod, gang? some people think is to attract lightning. what did you see here is to prevent lightning. if you got a lightning rod in this church, what you do is you leak off this charge that builds up as fast as it builds on, so you won't have a positive down here and the negative. they leak up, you see? and what happened, the lightning hit over here, you say, hit the bar room over here as it should be, right? the barn, okay? or something like that. but the church is spared if it has a lightning rod. so today it's common place to put lightning rods

on structures. the primary purpose? to prevent lightning. secondary purpose? if get belted anyway, the lightning will be guided to the ground and spare the structure. kinda neat, yeah? question. question? where does the voltage come from for lightning bolts. i mean, it's not just that they're with the positive and negative sort are just there. how does this-- your question really is, how is that does build up-- occurred in the clouds? how does the cloud get a negative on one part and a positive on the other? yeah. and you know what? that is still being researched. the last i heard there was still more questions than answers on that. some people tend to think that in this day and age, we know everything. we don't know anything, really, compared to what's coming along, huh? we don't yet-- as my understanding, don't really how to clear understanding of why you do get that voltage difference in a cloud to begin with. there's a lot of ideas as to rain falling down, friction rubs and sort of thing like that, but there's a lot of other questions unanswered. so i don't know really why you do get

that big difference in charge that causes this whole thing to begin with. there's several models for it as i understand. let's look at the granddaddy here. this is called the vandergraph generator. it's named after a person by the name of robert j.-- generator. all right. we'd be learning this stuff. all right. now, what we're gonna do here is talked about in the textbook. it turns out this belt is gonna carry charges from little lightning points here, deposit them up in here and will gonna build up an enormous charge on the top. let me show you what i mean. notice, i am, well--notice that i am keeping this closer to the dome than my head. guess why? [laughter] i don't want to put my head closer to than this, all right. now, let me show you that, that does charge. let's try this, gang.

[laughter] all right. let's try this. do we have anyone with nice long-- oh, my dear, back row, come, come. [laughter] all right. what i want you to do-- [laughter] could you touch that? it's safe. it's all right and i gonna take your support. stand over here, honey. what's your name? trisha. trisha. okay, trisha. take your right hand and put it on the dome. okay? it's all right. i'll take this away and you'll start to feel it's all getting charged. shake your head a little bit. okay. that's good, good. let it keep going, okay? do it like this. okay.

you see it starting to do what, gang? it start and do--stand up? could we have you people hold hands, please? could you hold hands? it's all right. hold his hand-- [laughter] okay. well, hold her hand, man. hold her to her hand too. she's nice. and hold her hand and maybe you hold back here. yeah, okay. hold hands. back here. keep going, right across the hall. let it cross. [laughter] you get it? i feel it. okay. thank you, trish. let's hear it for trish, all right? okay. there's one more thing i wanna show you, gang. as i wanna show you that i can light up this lamp

in the dark. robert, the lights, please. the lamp is lit. when i hold it like this, no. but like this, yeah. this, goes out. like this, light. i've got a question for you. lights please, robert. when i held the lamp like this, it lit up. when i held it like this, it didn't. surrounding this dome is a very strong electric field. i've got a question for you, where do you suppose the electric field is stronger, close or far? close. close? won't i have charges in here-- more energized here than here? when we talk about the energy per charge, we're talking about a concept called voltage. guess where the voltage will be higher, here or here?