Frostbite Theater presents... Cold Cuts! No baloney! Just science! Now, what'll happen if a person were to touch it? Or, maybe a better question is, "Should a person touch it?" [Audience] Yes! Well, maybe yes, maybe no. Do you guys know what voltage is? What does voltage measure? It's actually a measurement of energy per charge. Do you know how many volts are in a flashlight battery? One of those D-cells? [Someone in the Audience] One point five! One point five! Very good! How many volts in a nine volt battery? [Audience] Nine! Nine! That's why they call it a nine volt battery! How many volts come out of the wall? [Someone in the Audience] One hundred twenty! About a hundred and twenty. How many volts on that? When that thing's running well, it's about two hundred thousand. Okay, so think about this for a second. Can you safely touch a flashlight battery? [Audience] Yes. Yeah! Can you safely touch a nine volt battery? [Audience] Yes. Yeah! Can you safely stick your finger in the outlet? [Audience] No! No! So if you can't touch a hundred and twenty volts, should a person touch two hundred thousand? [Audience] Yes/no! Probably not. But, do you want to see it anyway? [Audience] Yes! That's what I was afraid of... [Audience] It's not on! I know it's not on. But there is something I am on that I don't want to be. The ground. What's this? [Audience] A stool. A stool made from... [Audience] Plastic! Which is an... [Audience] Insulator! I'm going to get on the stool. Not because I'm short, but because I want to get away from the ground. If I'm down here, the only insulation I have is whatever's in my shoe. Not that much. If I'm up here I've got my shoe, and I have nine inches of plastic? Something like that. Hopefully, hopefully it's enough insulation the electrons won't flow through me and into the ground. They'll just gather on me. If they just gather on me, what should happen? What hair I have left should stand up. Three... Two... One... Argh! Doesn't hurt. Anything happening? I'm hoping hair is doing something. But, at any rate, I'm not dead, which is a good start. Now, how many volts are on my left hand. [Someone in the Audience] A bunch. How much is a bunch? [Someone in the Audience] Two hundred thousand. About two hundred thousand. What'll happen if I touch the dome with my right hand at the same time? Argh! Nothing! Why does nothing happen? How many volts on my left hand? [Audience] Two hundred thousand. Two hundred thousand. How many volts on my right hand? [Audience] Two hundred thousand. Two hundred thousand. What's the difference? [Someone in the Audience] Nothing. There's no difference. Electricity flows from high voltage down to low voltage. If it's the same voltage, it doesn't move around. It's like having a bathtub full of water. If all the water's at one level, the water stays put. Have you ever seen birds land on the power lines? They don't get killed? Same reason. Both their feet are at one voltage. They might get a little bit puffy, but they don't get killed. Now, what would happen instead of this dome, I touch the grounding dome with my right hand. How many volts would be on my left hand? [Audience] Two hundred thousand. Two hundred thousand. How many volts would be on my right hand? [Someone in the Audience] Two hundred thousand. Uh, ground is zero. Defined as zero. What's the difference? [Someone in the Audience] Two hundred thousand. Two hundred thousand. That's like a waterfall. The electrons will flow from a high voltage down to a low voltage. In fact, if you listen carefully when I point at the dome... What's that sound? [Someone in the Audience] Electrons! Yeah, those are electrons flying off my finger. You'll notice... Watch my hair when I point. Why does my hair go down? Yeah, if the electrons are flying off my finger, they're not on my head to make my hair stand up. And you'll notice that also it doesn't do it when I make a fist, but it does when I point. It turns out charges jump off of points easier than they jump off of rounded things. That why these things are round, so they can gather the charge. Know what a lightning rod is? [Audience] Yes. What's a lightning rod? Pointy piece of metal. People think it's there to attract lightning. It's actually there to bleed charge away so lightning doesn't strike. In my pocket, I have that nail. It's like a lightning rod. If I let go of the point, if your ears are good, you can hear it whistle. If your eyes are good, you can see when I cover the point, and I let go of the point, my hair moves up and down. I don't know if you can see it, but I can feel it. I can feel it moving. It's more obvious, though, instead of pointing at the audience, if I point here. Okay, so again, why is my hair going down? [Audience] Losing electrons. I'm losing electrons! The electrons are flying off the nail to the dome. And, if I get it close enough, we can actually make a little spark that we can see better if Mr. Dave turns the lights off. A little spark. Lights back on. So that little spark tells you something. For there to be a spark there, the electrons have to come from the dome, through me, out the nail to that dome. If electricity's flowing through me, why am I not dead? [Someone in the Audience] You're insulated from the ground. I'm not insulated. That's the ground. I'm touching the ground. I'm not disappointed, I'm just confused. Why an I not dead? Well, I mean, if you like, I can come down here. What's my hair doing? [Someone in the Audience] Nothing. Nothing! Where're the electrons going? [Someone in the Audience] To the ground. Through my feet into the ground. If I get up here, I block them. So if electricity was flowing through me, why am I not dead? Again, this is not a major disappointment on my part. But, why am I not dead? Do you know what current is? Like in a river? What does current tell you? Yeah, which way and how much. Which way is the water flowing and how much water is flowing. For electricity, what does current tell you? Which way and how much. Right, is this a high current or a low current? It's low. That's why I'm not dead. There's just not that much electricity flowing through me. If this were a high current, what would happen? [Audience] You'd die. Yeah, I'd die, and in kind of a gross way. Have you ever cooked a hot dog in a microwave? [Audience] Yes. Ever forget to poke holes? What happens if you don't poke holes? [Someone in the Audience] It blows up. It blows up. Right, because the water inside changes to steam and it needs to get out somehow. Well, if this were a high current, the same thing would happen to me. My blood would boil and I'd blow up all over the room. It would be an experiment you do only one time. That's also why you don't stick your finger in the outlet. Even though the outlet is only a hundred and twenty volts, it's a high current. It's really the current that gets you and not really the voltage. Now then, what'll happen to my hair if I let go of the dome? [Audience] It goes down. Stay up, mostly. How come? I'm insulated! I'm insulated and there's nowhere for the electrons to go except from the water vapor in the air. If I want to get rid of it quickly, what do I need to do? [Audience] Step down. I need to step off. And as soon as I step off, I get a shock through my foot and the electrons leave me that way. By the way, this is how a lightning rod works. Here's your thunderstorm. You have a lightning rod. You bleed off the charge, lightning doesn't strike. Your neighbor doesn't have a lightning rod. They get fried. You're fine. They're not. You're fine. They're not. So, that's a little bit about charges and electricity and, again, it's why our machine works in the first place. Our machine...
Awesome!
That was a really good lesson. I wish he would have simultaneously related it to equations, since they are going to have to relate these concepts together with the symbology of the equation. Would help take some of the abstractness away and really drive home what these things are representing.
Ohm's law states that I = V/R
So voltage is related to currency and if there's more voltage then there's also more current, so why is there 200k volts but so little current? Is there a current limiter or something which causes the voltage to drop down if the current goes above a certain limit?
I learned some things
Where is this? Those are literal children,not a college class. what is this for?
TIL how a lighting rod works
Pretty nice, but I did not like his statement that current is what gets you, not really the voltage. Both are equally important.
I also think it is importent to convey the message WHY you can touch for example a car battery, while it is able to have a desastorous current flow, when you shortcut them. With that knowledge you are better to understand why both are important, current and voltage.
We need to poor like billions of dollars more into our public education systems, so that there can be more teachers like this guy
I love these high school level lectures. They make everything feel so accessible.