What actually is electricity?

 Introduction Focus Video Conclusions What's next? Authors

Introduction

To understand how electric vehicles work we’re going to need to know a few things about electricity first. Putting it really simply, electricity is all about pushing electrons around.

Focus

Let’s take a closer look at what electricity is and how making electrons move about is key. But what is an electron, I hear you cry…

Electrons

Electrons are one of the three particles that make up atoms – the other two are protons and neutrons. Neutrons get their name from being neutral. Protons and electrons, on the other hand, have charge. We say that the charge of the electron is negative; the opposite charge can be found in a proton, keeping everything balanced. We can abbreviate neutrons, protons and electrons to n0, p+, and e respectively.

The neutrons and the protons stay in the centre of the atom – we call it the nucleus – while the electrons whizz around the outside of the nucleus like orbiting planets (sort of – electrons get complicated very quickly, I’m afraid). Lithium – an element we will be talking about a lot in this series – for example has four neutrons, three protons and three electrons normally.

Normally there will be the same number of electrons and protons in each atom. This keeps the charge balanced – one negative for every positive! This keeps things stable and not much happens. Some elements, though, are quite happy to give away an electron and become positively charged overall. Others are greedy and can take electrons from other atoms to become negatively charged. Then there are the metals – they can share electrons out! Each atom in a metal can pass electrons to the atoms next to it and receive another electron as a replacement from somewhere else. This is what allows them to conduct electricity!

If you can make electrons flow, you have electricity.

Charge

Each electron has exactly the same amount of charge, and there is nothing that we can do to change that. All we can do is move the electrons from one place to another – and with them goes that charge! Moving the charge around is what we really want to do.

One or two extra electrons isn’t going to make a big difference but if we can build up enough charge we can start to do things with it.

Circuits

If you tried to just move electrons from A to B, then A would lose the negative charge from the electrons. All of that balance we had before would be gone and the positive charge from the protons in A that haven’t gone anywhere would start to really build up.

Remember before we said balanced charges are peaceful? Well if you get too much of a difference in charge between two things you’ll get sparks!

Sparks are beams of electrons moving from a negatively charged point to a positively charged one to cancel out all that charge and try and make things balanced again. Lightning happens when there’s a massive difference in charge between the clouds and the ground.

To be able to move electrons around without building up these massive differences in charge and get sparks we need to give the electrons a complete lap from A to B and back to A again. We call this a circuit.

Current

If you could see electrons and you were really fast at counting things you could watch a part of the circuit and count how many electrons whizzed past you each second. You’d be measuring what we call current. Current is the rate at which the charge is moving – so how many electrons are going past a part of a circuit per second. Current is how much charge is flowing.

Voltage

What happens if the electrons just aren’t flowing though? You’ve got a circuit, you’ve got electrons… what’s the missing ingredient? They just need a little push! Voltage is how hard electrons are pushed around the circuit. Voltage is also known as electromotive force – the force that is being applied to make electrons move!

Resistance

Some circuits are easier to move through than others. Imagine you have to get through an obstacle course… Some parts of it are going to be easy, like running across a field to the next obstacle. Some parts will be really tricky, like crawling through a tunnel or clambering up a rope ladder. The easy parts of the course don’t resist you much and you get through easily. The hard parts offer a lot of resistance and you have to really push yourself to get through. The circuits we try to push our electrons through are exactly the same.

Think of the things that you would use to make a circuit up – things like metals – these materials are easy for electrons to move around in. Electrons can conduct through these materials easily. Other materials that you probably wouldn’t add to your circuit – carpet, air, wood, slime – really make it difficult for electrons to move through! They don’t conduct electricity… in fact they resist it! Resistance is how hard it is for electrons to move through a material and is the opposite of conductance.

Making electrons move – making current flow

If we have a circuit that is easy for electrons to move around in (resistance is low) then we don’t need to push too hard for the electrons to start moving around. If the resistance goes up then we either need to push harder to get the electrons through at the same rate or that rate (the current) will drop. So current, voltage, and resistance are all linked together.

$voltage equals current times resistance$

Doing something with electricity – power!

Making electrons move doesn’t sound like a lot of fun, does it? But making a car move or a TV light up could be really useful. These things take some effort. Imagine pushing a car – that’s a lot of work! The charge of the electrons whizzing past a part of a circuit can be put to good use. As they are forced around the circuit and through a component like a motor they can give some energy to that component. The more electrons go through the component per second, and the harder they are being pushed as they go through it, the more work the component can do. For a motor, this means more power to spin the wheels and make the car move! We know the rate of electrons going through a part of the circuit as current and the force they are being pushed with as voltage, so now we can say that the power in the circuit is linked to the current and the voltage.

$power equals current times voltage$

Conclusion

Electricity is all about moving charge – usually electrons. If we can tame and control the flow of electrons – the current – by building circuits we can start to make the electricity work for us! The more electrons flowing around our circuit and how hard they are forced determines how much power our electrical system has.

What's next?

We now understand the basics of electricity! We know how to get enough power to push our car along and that’s great... but it can’t always be plugged in! Imagine how long the cable would need to be. We need a way to use it as we drive along.. How are we going to store all that electricity?

Find out in our next post!

Authors

The article and graphics were made by Dr Phil Jemmett.

Phil is part of the outreach team at WMG and is funded by the High Value Manufacturing Catapult research centre. He describes his job as being a ‘full time tinkerer’ and is either trying to build something, take something apart, or looking for the instructions to the thing he has just taken apart.