now i'm generating electricity to light up the lamp. see if you're sitting next to someone who knows how is it i'm able to generate electricity and light up that lamp by turning the crank. what is going on? okay, gang, how about it? how about it? what is going on? how am i generating electricity over here? what am i doing? what's faraday say you got to do? you have to have a magnet-- i gotta change the magnetic field intensity and some closed loop of wire, yeah? and guess what's inside here, gang? begin with closed loop of-- wire. --wire. and when i take a closed loop of wire and i rotate it, guess what i do to the magnetic field intensity? if i'm holding my arms out like this and it's raining, and the rain is coming straight down, foom, i threw my arms. i got a lot of rain coming through my arms, yeah? right. how about i turn like that, how much rain coming through? none. none. okay, how about i go like that some, i mean, i can't keep doing it, you see what i'm saying? but i could clip the amount of rain that i'm-- you see what i-- same thing over here.

in a magnetic field, you're rotating a loop. you're changing your magnetic field in that loop, honey, you're getting a voltage. and that voltage, light up the lamp. you see that, yeah? i mean, it's just not-- it's just a little gadget here. i want you to see what's going on with it, huh? okay. here's a piece of aluminum. aluminum, does it have magnetic domains in it? answer begin with a n. no. no, very good, okay. no magnetic domains. but watch this piece of aluminum, which is not a magnet now. is this the first time you've seen that? yeah. remember that. do you know how we put things in orbit, no? the way we put things in orbit is we take a rocket and we-- [grunts] --and it keeps picking up speed and finally goes into orbit, okay? but what are we going to do in the future?

well, you can't do it with people inside, gang. but if you wanna get something into orbit, okay, instead of a gradual acceleration where you pick up in speed, they'd be doing this. so, today, remember today is today's the day you first saw that. this is a very, very serious candidate for propelling things from the earth up into orbit. okay, yeah, electromagnetic propulsion. now why did this thing fly out, gang? should i leave that as a question for you? how many would have the next few days completely spoiled by not having that information? why did this thing fly out? why did this all of a sudden become a magnet? maybe there is no reason for that. maybe it's just one of the strange things about the world. well, let me ask another question. let me go like this. i held it way down here where the magnetic field is strong. let's suppose i just put it there.

electromagnetic levitation. how come that thing is levitating? why? this becomes a what when i plug it in? beginning with m. magnet. magnet. and this is levitating, so this must become a-- magnet. it's aluminum, but it's a closed loop aluminum. yeah. oh-- it's a closed loop aluminum in a changing-- starting to get it, starting to get it. let's see, this is a changing magnetic field 'cause it's ac. right. and there's some connection between the changing magnetic field and a closed loop. you guys be getting it? no, i guess there's no connection, or is there? how many know why this thing was levitating? did you ever see one magnet repel another? what did you just see now? you saw one magnet repel another. and why did it fly off when it was way down here? here's a question you can all answer. every one of you guys can answer this. this thing weighs an eighth of an ounce.

i'm making that up. an eight of an ounce. what is the strength of the electromagnetic force pushing up on that ring? check your neighbor. what's the answer, gang? eighth of an ounce. an eighth of an ounce. that's old mechanics, right? if there's an eighth of an ounce pulling down and there's something pushing up to be getting equilibrium, that up must equal down and that's an eighth of an ounce. ted bradstrom has some ideas of electromagnetic induction he wants to share with us today. speaking of electromagnetic induction. he's got a nice one here. really simple, really nice. magnet, coil. so we know when we're moving a magnet through the coil, what's gonna happen? hopefully we get current flowing, okay. it goes through the wire and meets another coil. what happens when you got a current through a coil? magnet. magnet, okay.

so we put a compass in the middle of this, and, okay, let's see if we get it. there we go. look at that, gang. look at that. an interaction from here to there. hey. just in case you think we were lying, i'll just move this and you can see how it's moving, right? is the-- nothing moves down there, yeah? no. now watch when he changes the magnetic field in the coil. what happened down here, gang? yeah, all right? okay. you want to know the fun part? you don't have to move the magnet. you can hold the magnet steady-- [laughter] yeah. --and move the coil back and forth. hey, you know what, you know what is a neat, neat application of electromagnetic conduction has just been the last few years, and that's the smart lights. when you're traveling down the road and you're coming through the traffic light, and the lights change for you. you drive over something, and that something changes the lights. i used to put, like, a piece of rubber tubing out there with compressed air and it would, boom,

make a little pulse of air, and that changed the light, but then the rubber would wear out. what they do now is they bury in the road a coil of wire, okay? a coil of wire buried in the road. now through that coil of wire is a magnetic field called the earth, and part of that field is in that earth, all right? now if you could change the magnetic field intensity of the earth through that big coil of wire, what would you induce in that coil? begin with a v. voltage. a voltage. ain't that right? so when your metal car drives-- or when your iron car, a wooden car won't work. when your iron car goes over that coil of wire, does it not alter a little bit the magnetic field intensity in that loop? the answer begin with a y. yeah. and when it does that, it makes a little tiny electric current, which activates the switch of changes and changes the lights, isn't that neat? so the next time you're driving near traffic lights,

look down to see if someone hasn't put down there a couple of coils of wire, 'cause you get two to make sure, huh? check that out. another thing, too, tape recorders. tape recorders. what does a tape recorder do? well, in the tape recorder-- when you speak into a microphone, you get a little plug like ted had, you go back and forth, back and forth. it makes a little vibrating current in wire, right? what if that is passed down to a little electromagnet and you drag by that electromagnet some rusty tape. and the rust is iron oxide. when that iron oxide slides by that magnet there varying strength, you'd get on that tape then varying strength of magnetism. some as magnetized a lot, some magnetized a little bit. and the little vibrations you're getting on the tape. now you take that tape, bring it to another machine, i wanna tell you the same machine, and drag that tape at the same speed, pass an empty coil of wire, what's gonna happen

to the magnetic field intensity in an empty coil of wire when that tape drags by? it's gonna change. it's gonna change, ain't that right? right. and if a piece of tape comes by that's heavily magnetized, boom, you're gonna get a big pulse of current. a little tiny bit, a little tiny-- well, you can get variations. and isn't it amazing that that tape driving by there, the empty coil, the variations in the magnetism set up variations of voltage in that wire, faraday's law, which then goes into driving the speaker. again, the plug going back and forth glued to a what? a paper cone, and the paper cone vibrates the same way, mm, and you get music. so next time you look at your tape recorder, honey, what's underlying all of that? it's emi, what are talking about? electromagnetic induction. ain't that neat? now i got one question to leave you with--

i got two questions. number one was, how do this thing, foom, fly off? what's the basis of that electromagnetic levitation? and the other question is, is when i crank this generator, it's harder to turn when it's lit up and easier to turn when it's not. right now, i'm turning only against friction. but when i hook it in, it becomes part of the circuit, it really is more difficult to turn. hc, how come? think about that. it's physics, all right? yeah.