Avoid electric shock getting out of a car!

Avoid electric shock getting out of a car!


[MUSIC PLAYING] [MUSIC PLAYING] [ZAP] I hate that! Why do you get shocked sometimes
when you get out of your car? Or when you touch a doorknob? Or when you take off a
sweater and hug someone? And is there a way
to not get shocked? To prevent this
from happening, you have to figure out
what’s happening. So this is called a Van
de Graaff generator. I use it a lot in
science demos for kids. It’s a machine that builds
up a ton of static charge– that is, a bunch of positive
charges on the outside of this metal sphere– so
that when I bring this smaller grounded metal
sphere close to it, it discharges through
the air in a giant metal spark that will shock you. Ugh, I hate that. The kids love it. So this is where it gets fun. If I put a metal pan on top of
the Van de Graaff generator, it should take on the same
positive charge as the sphere because it’s conductive. But like charges repel. So when I turn this on,
the pan should– fly off. And it does. Now one kid saw
this and asked what would happen if we put the
Styrofoam ball she was holding on top of the generator. Let’s try it. But I told her probably
nothing would happen, because Styrofoam
is an insulator. So I assumed there’s no way
you can pass charge to it. Let’s see. I stood there confused. Insulators don’t conduct
electricity, right? So how can you charge them? Well, in fact, it’s very easy. This balloon– is now charged. See? And this tape is now charged. See? And these are both insulators–
just not perfect insulators. In very violent
events, electrons from the atoms in one material
can get stripped off and passed to another material, causing
both materials to become charged– this one positively,
because it lost electrons, and this one negatively,
because it gained electrons. Even if they’re
usually insulators. And for the poor tiny atoms in
these materials, rubbing them together would
definitely be considered an unsettling violent event. Now back to the car. The violent event here is
when you get out of the car, you slide across the seat,
and both you and the seat become charged. And now some of that charge will
leave your body into the air. But if the air is cold
enough and dry enough, and you touch the
metal soon enough, that charge will quickly leave
your body into the metal, and you will feel that. And you’ll hear it,
too, as a shock. [ZAP] So do you prevent
this from happening? Well, don’t keep
yourself isolated. As you get out of the
car, touch the metal on the side of the car. And even if charge is
building up on you, it’ll continually
flow into the metal. And it won’t build up
enough on you to shock you. Problem solved. Either that, or rub yourself
all over with dryer sheets. I don’t know if that works. Someone please try
it and let me know. So now for this insulator,
there was no violent event. Or was there? [CONTINUAL ZAPPING] See, air is usually
an insulator, too. Which is why you’re not
shocked by your outlet until you stick metal in it. Air is an insulator
until the voltage, which is related to the amount
of surface charge on here, gets so high that electricity
can travel through the air. Electrons are stripped
off of the air molecules along the way in
a process called ionization, which releases
light, and you see a spark. But you have to get the
voltage really high for this to happen, so high
that overcomes the insulating
properties of air. So high that it overcomes
the insulating properties of Styrofoam, and the Styrofoam
takes on a surface charge that repels the metal sphere. Large enough for the insulating
plastic on this pom-pom to repel itself, so that they
stick up– at least on the top. On the bottom,
there is more going on where the pom-pom
sticks to the sphere, and it has to do with
electrical induction. But we’ll leave that
for another video. Thank you so much for watching. I’m going to see if I can get
my hair to stand up, if there’s not too much moisture. Although it rained today,
and it’s pretty warm. Nothing’s happening. It’s too humid, and this
thing’s not big enough. It’s gonna shock me. Ah! [CONTINUAL ZAPPING] It didn’t! [MUSIC PLAYING]