- How does a battery work?
Well, it's surprisingly simple.
It just uses the chemical reaction
between the battery acid and two different metals
to make one side have too many electrons, the negative side,
and one side have too few, the positive side.
Wait, how does that make a battery work?
And how does a battery create current?
Well, I'll tell you, and along the way,
I'll tell you why some materials conduct electricity,
and some materials don't,
what current actually is,
and how every electrician and scientist in the world
is lying to you.
Also, I'll tell you the importance and meaning
of free electrons and ions.
Don't worry, it's surprisingly simple for chemistry.
Ready?
Let's go.
♪ Electricity, electricity ♪
- In order to understand how a battery works,
and what current is, I need to define two terms,
free electrons and positive ions.
In order to do that, let's start with the basics.
Objects are made of atoms.
Atoms have a heavy, positively charged center, or nucleus,
and have a cloud of negatively charged electrons
that are stuck, or bonded to the nucleus.
If that was the whole story,
then we would have no current or electricity.
However, certain elements
don't hold on to their outer electron very strongly,
and the electron can escape the pull of the nucleus,
and basically roam free.
This is called a free electron, good name, hey?
When the electron escapes,
the atom is left with more positive charge
than negative charge, and it is called a positive ion,
To recap, electricity depends
on negative tiny free electrons
that aren't stuck to any particular atom,
and heavy positive ions,
or atoms that have lost an electron or two.
Current is made of flowing electrons.
That's all current is.
Now the individual electron doesn't move very far,
but it basically sets up a wave of electrons
moving in generally the same direction.
Metals have a lot of free electrons and ions,
so electrons can flow easily through them,
and they are called conductors.
Plastics have very few free electrons and ions,
so that electricity cannot flow through them easily.
They're called insulators.
This is why a wire's made of metal
for the current to flow through
with plastic insulation to keep the current
from flowing out of the wire into say, your hand.
So how do you get electrons to move in a metal?
One way is to use a battery.
Look at any battery.
It always has a positive side and a negative side.
The negative side has too many electrons,
and the positive side has too many ions.
Opposite attract, and like repel.
So the negative electrons
want to get away from the negative side,
and are attracted to the positive side.
If you connect the sides with a conducting wire,
the electrons will flow from the negative side,
and into the positive side.
Side note, I'm about to blow your mind.
You might've been told the current flows
from positive to negative.
That is because Ben Franklin
came up with the idea of positive and negative charges
way back in 1745.
At the time he arbitrarily,
and insistently stated that electricity,
or as he put it, electrical fire,
flowed from positive to negative.
It took over 150 years after Benjamin Franklin
before we discovered the existence of the electron.
By that time, we had equipment, and classes,
and rules, assuming current flowed
from positive to negative.
So instead of reversing all electrical equipment and rules,
they decided to just, well, ignore reality.
We say current flows one way,
when what is really going on
is that the electrons are flowing the other way.
In other words, whether we realize it or not,
every science teacher and electrician in the world
is lying, crazy, right?
Okay, but I still haven't told you how a battery works.
How does a battery create,
and maintain a positive and negative side?
Well, every battery uses the chemical interaction
between two types of metal, and then acid and a base.
Acids have a chemical reaction that moves the free electron,
and bases have a chemical reaction
that move the positive ion.
But either way, they leave the positive side
with too few free electrons,
and the negative side with too many.
The original battery built in 1800
was just strips of silver and zinc
in a cup full of saltwater as the acid.
This made a very weak battery,
but the saltwater would react with the zinc
to add electrons,
and react with the silver to remove electrons.
Soon, people were making batteries
with plates of different metals in a bath of acid.
In fact, the modern lead acid car battery
is made of just plates of lead and lead oxide
in a pool of sulfuric acid.
However, acids are an inconvenient chemical,
as strong acids tend to eat away
at the outside of the container,
and as liquids, are easy to spill.
In 1899, we started using bases
instead of acids as the chemical inside a battery.
And now most modern batteries
use a chemical base instead of a chemical acid.
There are many types of batteries used today,
but let's look at a typical alkaline battery.
Alkaline batteries get their name,
because alkaline is another word for base.
Chemists often have many words for the same thing.
Drives me nuts.
Anyway, alkaline batteries come in many shapes and sizes,
but inside, they all tend to have same metals,
and chemical reactions.
So let's look at what's going on
inside a typical alkaline battery.
Inside a battery,
there's a column of ground zinc,
mixed with the base chemical potassium hydroxide.
Surrounding the zinc is a different metal,
called manganese oxide.
The potassium hydroxide chemically reacts to the zinc,
and removes positive ions,
leaving that side with too many free electrons,
and the net negative charge.
The chemical also reacts to the manganese, and adds ions,
leaving that side with too many positive ions,
and a net positive charge.
The zinc and manganese are separated by a plastic sheet,
so that the electrons don't just flow over
to the positive side with the ions.
Therefore, the electrons in the zinc side are stuck there.
They move as far away as they can from each other,
and congregate on a nail called a current pickup.
This reaction occurs until charges on both sides
create such a strong electromotive force
that the chemical reaction stops occurring.
In a typical AA battery, that's 1.5 volts.
When the battery is placed in a circuit,
where electrons can flow in a conductor
to the positive side of the battery,
the chemical reactions occur again
to keep the electromotive force at 1.5 volts.
When the chemicals react to the metals,
the chemical becomes less powerful.
Over time, the chemical loses its power of reaction,
and the zinc runs out of ions to move.
At which point, the battery is dead.
Alkaline batteries are not rechargeable batteries.
However, rechargeable batteries work the same way,
in that a chemical moves over ions or electrons,
so that the positive side has too many positive ions,
and the negative side has too many electrons.
However, rechargeable batteries
reverse the chemical reaction
when current is forced through them in the opposite way,
so that the ions move back to their original metal,
and the chemical base or acid becomes stronger again.
Different batteries use different geometries,
and different chemicals, and different metals,
but they all use either an acid or a base,
and two types of metals or metal compounds
to make one side have too many electrons,
and one side have too many positive ions.
And that's how a battery works.
Told you it was simple for chemistry.
♪ Electricity, electricity ♪
- Thanks for watching my video.
Please remember to give it a thumbs up.
It's always a nice thing to do.
Also, I'm making a whole series of videos
on the secret history of electricity.
So if you are interested in how, for example,
Benjamin Franklin came up with the whole idea
of positive and negative charges,
that is video number eight, how Benjamin Franklin
discovered the true nature of electricity.
If you are interested in the discovery of the battery,
that is a great story involving dead frogs and jealousy.
Those are videos number 11 and 12.
Check it out.
Either way, you should subscribe to my channel,
called Kathy Loves Physics,
my Facebook page, called Kathy Loves Physics,
or my website, www.kathylovesphysics.com.
Have a good day.
(soft music)