Electricity

Electricity is all around us, and is vital to our modern world.

electricity

It powers our houses, lights our world and runs our computers.

But what is it?

Force

Electricity is a force.

It is one of the 4 basic forces of the Universe.

The idea behind all of electricity is:

charge repel attract

Fundamental particles can have +1 or −1 electric charge:

We sum it up by saying:

Like charges repel, and opposites attract.

 

electron charge

 

Electric charge can be felt far away (called an electric field).

In fact there is no limit, but it does get weaker the further we go.

Now let's find out more about these fundamental particles

Atoms

An atom looks like this:

atom hydrogen quantum
Quantum Microscope Image of an Atom
http://dx.doi.org/10.1103/PhysRevLett.110.213001

To understand it better let's have a simple illustration (but atoms are not really this neat):

atom with electrons and nucleus

In the center are protons and neutrons, and around them dance the electrons:

benjamin franklin

 

Using + for protons is just history from when Benjamin Franklin studied electricity in glass jars.
We could swap over + and − everywhere and it would still work out fine!

 

An atom naturally has the same number of protons and electrons, and is in balance.

But electrons can be knocked off!

atom positive charge
Our atom loses an electron and is now positively charged
(Try adding up the + and − left behind)

So we now have a positively charged atom, and a negatively charged electron.

We can make that happen ourselves:

static balloon

Example: Rub a balloon on your hair

• Rubbing the balloon makes it pick up lots of electrons, and it becomes negatively charged.

• The hair loses electrons so becomes positively charged.

The balloon now has a lot of negative charge. And your hair has lots of positive charge. 

Opposites attract, so the + is pulled towards the − and your hair stands on end!

static ballon with dog hair

 

I tried this on Arrow the Dog.

The invisible force of electric charge really did pull his hair and the balloon together.

And he seemed happy about it, too!

You may have seen or felt this yourself when a sweater clings to a T-shirt, etc.

We call this "Static Electricity" because most of the time it just sits around (static meaning not moving).

Static Discharge

finger spark

But be careful!

If you build up a big difference in charge it can suddenly bring itself back in balance with a spark.

The sudden release is called electrostatic discharge, or simply static discharge.

A dramatic example is lightning.

lightning to ground

In storm clouds the charges get separated when water droplets and ice crystals are pushed around by strong winds (updrafts, downdrafts, etc). Negative charges tend to be near the bottom of the cloud:

storm charge diagram

Each little charge has its little electric field, and they all add up to make massive electric fields, which can concentrate charges on the ground.

Have you ever noticed during a thunderstorm that the air feels different?

Eventually the charge difference gets large enough and *kapow* lightning!

Lightning happens between cloud and ground, but also within the cloud and between clouds:

lightning between clouds

Lightning is bright because the air gets heated up to around 50,000 °C (it becomes a plasma), and the resulting shock wave causes the thunder.

If you are within a few meters the thunder goes "crack" (I have heard it twice) because it breaks the sound barrier. Further away it makes the classical bang and rumble.

Current

Static discharge (such as lightning) is violent and not very useful.

What we want is a continuous flow of electricity called a current.

It is called current because it is similar to a current of water:water current

But how?

Using magnets!

Electricity and magnetism are linked, and are together called electromagnetism:

electro magnetic field properties
A changing magnetic field produces an electric field.
(and a changing electric field produces an magnetic field, too)

 

Simply moving a magnet past a wire makes electrons move along the wire (press "Move"):

 

 

Notes for the curious:

 

So moving a magnet past wire makes current. We have our flow of electricity!

But when the magnet stops moving, so does the current.

So how do we keep the current flowing? Rotating the wire in between magnets is a good solution:

magnet wire rotate

To make even more current flow we can have lots of loops of wire (called winding), and make everything huge, like this:

generator stator
Part of a large generator
From Wikipedia user Astronomyinertia

And that is how we get large flows of electricity to power our homes and industry.

Conclusion

 

NOW I suggest you go back to the start and read this all again so it makes more sense.