Main content
Course: MIT+K12 > Unit 1
Lesson 3: Physics- The physics of skydiving
- The physics of invisibility cloaks
- The science of bouncing
- How do ships float?
- Thomas Young's double slit experiment
- Newton's prism experiment
- Bridge design and destruction! (part 1)
- Bridge design and destruction! (part 2)
- Shifts in equilibrium
- The Marangoni effect: How to make a soap propelled boat!
- The invention of the battery
- The forces on an airplane
- Bouncing droplets: Superhydrophobic and superhydrophilic surfaces
- A crash course on indoor flying robots
- Heat transfer
© 2024 Khan AcademyTerms of usePrivacy PolicyCookie Notice
The invention of the battery
The invention of the battery with Alessandro Volta and Luigi Galvani. Created by MIT+K12.
Want to join the conversation?
- what does "like to go swimming" and "like to stay dry" implies. I mean, do the electrons like to go swimming? Except this point, the video gives an awesome intuition...(58 votes)
- The "like to go swimming" (LTS) vs. "like to stay dry" (LTD) metals refer to the natural state of the electrons in the atoms of the material. The LTS metal refers to the An-ion (the Dogs). Just like in the video, there are easily removable electrons in the outer valence shell of the atoms of this metal. It likes to get rid of them in order to stabilize its electron state. How does it do this? Well it just so happens the LTD metals, called Cat-ions, are electron deficient in their atoms' outermost valence shells. That means that just like the cats in the video (did you get that joke?), they need extra electrons and will be more than happy to scoop them if there is a path between the two metals on which the electrons can flow. That's where the wire comes in, or in the case of the video, the tube with the mini-Reese's.(60 votes)
- Why exactly choose zinc and copper? What are some of the metals that can perform the same task?(38 votes)
- In order for a current to be established between the two metals, you have to create a voltage difference between them. We do that by finding metals that want to give up their electrons to greater or lesser extent when exposed to the electrolytic solution. The greater that difference, the more evident the "battery" effect. Copper and zinc are a good choice because there's a big "drop" between the two and because they're easy to find around the house!(25 votes)
- I so understand this. When Zinc runs out of electrons, the batteries run out of power!(13 votes)
- It doesn't necessarily "run out". There is simply no charge differential between the elements.(5 votes)
- At6:53, they mention that to make a homemade battery you need something salty or sour. Why is this necessary to get the electrons flowing in the battery? What is the equivalent of these materials in batteries we use in our daily lives like those found in remote controls, phones, or cars?(5 votes)
- In order to close the electrical circuit, charge has to flow between the two pools, because otherwise the "Zinc" pool will accumulate positive charge (excess of positively charged "dogs") and the "Copper" pool will accumulate negative charge (depletion of positively charged "cats"). Unfortunately they did not mention this in the video.
In salty or sour solutions there are plenty of ions (positively and negatively charged particles) which can provide the balancing flow between the pools. The pools have to be connected by a "salt bridge" (thin tube filled with a solution containing ions) or a membrane through which ions can pass.
In ordinary batteries e.g. a piece of porous cardboard plays this role. Look here: http://en.wikipedia.org/wiki/File:Dry_cell_(PSF).png(7 votes)
- Where can I get copper without buying it?(6 votes)
- Try pennies! They work just fine, and the copper is actually worth more than the penny itself (1 cent) so don't hesitate to use them in experiments.(1 vote)
- At7:05, what is the song played on the tiny speaker? It sounds like something from the Hotline Miami OST.(3 votes)
- It is from Grandia I. I think. Look up Grandia 1 desert music and check the link:
https://www.youtube.com/watch?v=9KvgXfsb4Hg
Actually, it seems only similar. Check it out.(2 votes)
- When Zinc runs out of electrons and all the dogs are in the ocean, is that when the battery dies? or runs out of juice? Also, he said you could use ammonia, isn't that in urine?(4 votes)
- That makes sense because the flow of electrons stops which means there is no current.
Urine is not ammonia. The smell that you get from urine is caused by the release of ammonia.
I hope this helps!(3 votes)
- How long will a battery like that last.Can you recharge it if it goes dead.(3 votes)
- it might take a hour or two ps. im sorry if im wrong(2 votes)
- what happens to the zinc when sending the electrons? zinc doesnt have infinite electrons so does that means it becomes more and more positive until there is an equilibrium of electrons between the two metals and then the current stops?(3 votes)
- The only reason Zinc can send electrons is because there is a potential difference.
Yes, you can have an infinite amount of electrons, but that means you also have an infinite amount of protons on the other end waiting to cancel and neutralize each other. But, lets say its finite, because there is only a finite amount of Zinc.
And you got the last part CORRECT:-), that pretty much how generation of electricity stops.(1 vote)
- How did that guy remove the frog's leg. How long has it been since he took it out?And can you create a battery from metals other then zinc and copper?(2 votes)
- "If the nerve that passes that signal around is damaged, or the hopping muscle tissue around it is damaged, then it won't work any more! This will happen eventually - and usually within a few minutes." - So, the guy probably removed the frog leg quite recently.
"In order for a current to be established between the two metals, you have to create a voltage difference between them. We do that by finding metals that want to give up their electrons to greater or lesser extent when exposed to the electrolytic solution." So yes, you can create a battery from metals besides zinc and copper. And in the video, at7:16they guy talks about other types of batteries.(3 votes)
Video transcript
Greetings, fellow thinkers. I am Alessandro
Volta, and today I invite you to join me on
a journey of discovery. Together we will relive
my greatest triumph, the invention of the battery. Ah, but you say, this doesn't
look much like a battery. Perhaps you were expecting one
of these, or even one of these. But my reply is this-- all
these batteries are the same, and they only require
one thing to make them work, a flow of electrons
from high concentration to low concentration. This simple idea
powers flashlights, computers, and even
tiny little helicopters. Come, meet my colleague,
Luigi Galvani. It is upon his
research that I based my most important discovery. (SINGING) Frogs, frogs, frogs. You've got to cut them
up, to see how they work. Frogs, frogs, frogs. You got to cut them up,
to see how they work. Galvani, how are you? Oh, Volta. Perfecto timing for a lab visit. I've just received an amazing
new piece of equipment, a set of pinchers where
one part is made of copper, and the other part
is made of zinc. And using these pinchers, I'm
going to dissect the frog. Oh, indeed. Would you be so kind as
to demonstrate for me? Gladly. Whoa! Behold, electricity. From the tissues of
this humble beast, I've evoked an electrical fire. Amazing. With this power, we could
drive electric carriages, and electric boats. And if electricity
resides in a single frog, we could feed one
frog to another, and the second to a third,
and a third to the fourth, and make a gigantic frog, full
of fiery electric potential. Ah, but you're wrong,
my dear friend. You've made a
magnificent discovery, but you misunderstand the cause. Well, where does the
electricity come from? Well, you're using
tools that are made out of two different
metals, zinc and copper. This is the source
of the current. If we were to use tools that
are made out of the same metal, nothing happens. See? But with my pinchers of
zinc and copper-- amazing. Amazing. This is truly a
wonderful discovery. Thank you, Volta. But now you've got me thinking,
why does electricity flow from one metal to another? What makes copper
and zinc different? Ah, I'm so glad you asked. Let me tell you a tale,
a tale of two metals, a tale about swimming, and
a tale about cats and dogs. Here we have zinc, a metal
that is made of dog atoms. All of his dog atoms
love the ocean. They'd do practically
anything to go for a swim in the salty water. And here we have his friend
copper, who is covered in cats. All of his atoms are cats. They hate the ocean, and
want to get out of the water as soon as possible. Whenever a dog hops
into the water, it has to leave two of
its electrons behind. What am I going to do with
all these extra electrons? And in order for a cat ion
to get out of the water, it's got to find two electrons. Hey-- hey, get us
out of the water. We hate swimming. I want to help you, but
I have no electrons. Hey, it's cold in here. Can't you get us dry
without electrons? Nope. It takes two electrons to
get you out of the water. But let me call my friend, zinc. He may have extra electrons. Hello, zinc speaking. Zinc, it's copper. Oh, man. Did you know that I was
just about to call you? Really? Hey, listen. Could you do me a favor? Do you and your dog ions have
any extra electrons around? That is so crazy. I was about to call you, because
I have all these dog atoms. And every time they
go swimming, they leave behind two electrons. So now I have tons of electrons,
and I don't know what to do. And honestly, I'm
feeling pretty negative about the whole situation. Well, I'm positive we
can find a solution. Why don't you send a couple
electrons through the wire, and that way I can pull some of
my cat ions out of the water? Right on, man. I'll send them
through two at a time. Oh, my cat's purring. It loves being out of the water. Hey, zinc, do you have
any more electrons? Oh, totally. In this way, the two friends
are able to share electrons through the wire, creating
an electric current. The zinc dogs want to swim, the
copper cats want to get dry, and that's what makes
electricity flow through a battery. Here's the zinc, whose atoms
are like dogs and want to swim. And here's the copper,
whose atoms are like cats. And here's the wire
through which zinc sends its extra electrons to copper. This flow of electrons is
called an electric current. You can use that current
to power a light bulb, or a speaker. Or a frog's leg. Electrons flow from the
zinc, through the frog's leg, and into the copper. The nerve in the frog's muscle
is sensitive to electricity, and it flexes from the current. Now I understand. The electricity isn't
generated in the frog's leg. Rather, electrons leaving zinc
and traveling into the copper carried the current. Mm-hm, mm-hm. And if you wanted to
make your own battery, all you need are
two kinds of metals, a wire, and something
salty or sour. Here's one that I made. We have a zinc nail,
a nice bit of copper, and this beautiful winter gourd. I'm using it to power
the tiny speaker here. Oh-- oh, that's good. I made my famous batteries
with zinc and copper, but other metals
would work, as well. Lithium batteries
are in cellphones, and lead batteries are in cars. And instead of a
gourd, you could try using really salty water,
or potatoes, or vinegar, or even ammonia. In every case,
there's two metals, one which likes to go
swimming, and the other one, which likes to stay dry. And the difference
between the two of them allows the electrons to flow. Oh, hey, buddy. What's wrong? You made a wonderful
discovery toay. Yeah, I know. But I just got totally
emotionally wrapped up in this idea that we could
use frogs fed to each other to power the world. And now I realize that
the data says otherwise. And so I guess I have no
more need for these guys. Godspeed, frogs. Adieu.