Should a Person Touch 200,000 Volts? A Van de Graaff generator experiment!


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…

100 thoughts on “Should a Person Touch 200,000 Volts? A Van de Graaff generator experiment!”

  1. Love how a lot of people said yes to the teacher touching the electric ball like there is no regret in him touching it

  2. I get that if there is a lot of energy per charge and there is barely any charge flowing through you that it won’t really harm you. But each coulomb flowing through his body has energy comparable to pushing a small ball with a 1 pound net force 147512 feet. Surely the amperage must be a fractional of a coulomb per second I presume.

  3. If he actually had 200,000 Volts across his body he would be dead. 200,000 Volts over a person with a resistance of like 1000 Ohms would give 200 Amps according to Kirchhoffs Law.
    30mA is enough to kill a person.

    He is not touching 200,000 Volts 🙂

  4. Whats the Current limiting factor ? If i got a high enough Voltage, high current is able to flow through my Body resistance. Voltage could be Current Limiting in a Way but in this Case its not. So is the Capacitance of the Tower so low, that some current is able to flow through Air but not, or at least not much through the Body ? sry bad english

  5. I'm a little confused here. I = U/R (curent = Voltage / resistance). I google and it says electrical resistance of human body is usually 100,000 ohm at max. So in this case, the current going through his body would be 2amp, which is 10x more than lethal level.
    What am I missing here?

  6. Thanks for teaching me how a lightning rod works I always thought they gave the lighting a path to earth ground when it strikes.

  7. Sir i didn't understand why you didn't get shock from van de graph generator. please will you explain in more easy way 🙂

  8. It might be more appropriate to say that power/energy kills – not current or voltage. The electrical potential is only 200,000 V when he is not touching ground! The voltage and current plummet when he is grounded. The actual amount of electrical energy sent across his body is small, even if there is a high initial inrush current.

  9. Is his explanation of lightning rods really correct? In his example, the screw driver provides a low resistance path to ground, which prevents the van der graaf from developing the electrical potential needed to arc across the higher resistance path of the ground ball.

    I don’t think that’s quite applicable to a lightning rod. Lightning rods are a lower resistance path to ground. In that sense the analogy is correct. However, lightning rods don’t continuously pass current and discharge the atmosphere like the screw driver continuously pass current and discharge the van der graaf. That would be like saying lightning rods prevent lightning strikes in an area. They obviously don’t.

  10. What every college professor teaching these basics should do. Using these materials helps otherwise it wouldn't be in the classroom.

  11. As a student in europe qe dont get these types of fun experiments a s study halls , we just have classrooms

  12. Am not an engineering student neither do I know anything about electricity like they do, but what I saw today in this video was AMAZING…
    I learned a whole 8 mins of engineering and am wowed☺

  13. If voltage is more i.e. 20000V, then the Current will subsequently be high (as I=v/r). Then why you not get electrocuted?

  14. 🇮🇳🇮🇳🇮🇳* Wish it was thought like this in India, RESPECT TO ALL GOOD PHYSICS TEACHERS ALL OVER THE WORLD ESPECIALLY INDIA BUT STILL FEEL THAT WE REQUIRE MORE PRACTICAL DEMONSTRATIONS INSTEAD OF JUST EXPLAINING THEORIES* 🇮🇳🇮🇳🇮🇳

  15. When I was in high school my teacher did this as well. He forgot to discharge the balls and after class I wanted to hand in a paper. I reached between the two balls.

    I then learned what 200,000V feels like.

  16. Difference between Indian education and other! We have studied the same also passed with high percentage but not like this intrestingly

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