Hi Gang! You've probably all seen the trick where you
rub a rubber balloon against your hair
and then you put the balloon on a wall, the balloon then sticks to the wall.
The balloon gets charged by an effect called the triboelectric effect.
Not all materials will work and which two materials you use together is
important too.
The list of what materials work is called the triboelectric series.
Here's a short list with some materials. The order of the materials in the series is
very important. Some are on the positive side of the list
and some are on the negative side. Also, the farther apart the two materials
are in the series, the better it works.
So rubber, like our rubber balloon,
is far apart from hair, so they work well together.
But amber and wool are very close together and won't work as well.
Here's a piece of vinyl which I cut from some old window blinds.
And here's a glass. You can see that vinyl and glass are far apart
in the triboelectric series so they should work well together,
just make sure you clean the glass first. We want glass, not grease or dish soap.
To see if it worked, I'm using a homemade electroscope.
If the two aluminium foil leafs in the jar spread apart then it worked.
And sure enough, the leafs spread apart. It worked.
So how does it work?
Let's use our vinyl and glass example. We'll go right down to the individual molecule
level.
A molecule is simply a collection of atoms bonded together.
Vinyl is made up of hydrogen and carbon atoms and glass is made up of oxygen and silicon
atoms. Though it's not too important to know which
atoms are involved.
If we add up all the parts of the atoms, vinyl is made up of 15 positive protons and
15 negative electrons. Glass is made up of 66 positive protons and
66 negative electrons.
If there are the same number of protons and electrons in a molecule
then the molecule is neutral. It's neither positively charged nor negatively
charged.
Now what happens if we bring the two molecules together,
like we were doing when we rubbed them against each other?
When they get close enough they form an electrochemical bond.
It's as if we formed a new, bigger molecule.
But most importantly, when the bond is formed,
electrons move from the glass molecule to the vinyl molecule.
In this case three electrons are changing places.
As a result, the vinyl now has 18 negative electrons,
since that's where the three electrons went. And the glass now has 63 electrons,
since that's where the electrons came from.
Since the vinyl now has more negatively charged electrons
than it has positively charged protons, the vinyl is negatively charged.
And since the glass now has more positively charged protons
than it has negatively charged electrons, the glass is positively charged.
And if we then move the molecules apart again, the electrons don't go back to where they
were. The vinyl stays negatively charged and the
glass stays positively charged.
And that's what's happened when I rub them together.
The molecules are repeatedly forming bonds, then moving apart,
forming bonds, then moving apart. The more I do this,
the more electrons move from the glass to the vinyl.
And the more negatively charged the vinyl becomes,
and the more positively charged the glass becomes.
And now you see why vinyl is on the negative side of the triboelectric series
and glass is on the positive side of the triboelectric series.
Rubbing vinyl with glass make vinyl negative and glass positive.
Humid air makes is harder to charge things up.
Dry air is better. This is a relative humidity meter bought from
a local hardware store. It's at 30 right now
and I was able to charge the balloon and glass. But when it's at 80 things don't charge up
as much. So if you're having problems,
that may be the reason.
Here are some other things to try.
Rub your socks on carpet and you'll often get a shock when you touch
someone or a metal door handle.
Run a plastic comb through your hair. Or, rub a plastic soda bottle against your
hair. Some other examples are
that a car sometimes gets charged and you get a shock when you go to touch the
door handle. And the non-metalic rollers and belt of a
van de graaff generator are charged by triboelectricity.
And if you need to look up some materials, you can find a more complete triboelectric
series table on my website here.
There's also a link to it in this video's description.
And lastly, why did the balloon stick to the wall?
As I said, the part of the balloon that I rubbed against
my hair became negatively charged.
The wall, however, is neutral, same number of positives as negatives.
But like charges repel each other, so the negative charge of the balloon
repells some of the negative charge on the wall
deeper into the wall, leaving a more positively charged surface.
And unlike charges attract each other. So the negatively charged area of the balloon
is attracted to the positively charged surface of the wall.
Well, thanks for watching!
See my youtube channel, rimstarorg for more informative videos like this.
That includes one on how to make your own electroscope.
Another on how a Van de Graaff generator works. And for variety, one on using nitinol wire,
a shape memory alloy, to make an inchworm walk across a table.
And don't forget to subscribe if you like these videos,
or give a thumbs up, share with your social media,
or leave a question or comment below.
Bye for now!