These days, everything depends on electricity – from the tools on which we work to the places where we get our entertainment. Everything seems to be powered and charged, plugged in, connected to the mains.

We use electricity literally all the time. And so we take for granted the fact that it comes straight into our house, until it is right there in the wall next to our bed, sofa, or desk.

And whilst we no longer appreciate quite how amazing this is as an infrastructure, many of us probably don’t know much about the technology that all this is dependent upon. This is the transformer, a piece of electromagnetic equipment that facilitates electricity’s journey from power station to plug socket.

Without it, we’d have none of the things that are so normal in our daily lives. In fact, we’d have nothing electrical in our homes at all.

That’s why we need to take the time to learn about these simple little things, these ubiquitous little contraptions. Because without them, we’d still be living in the conditions of the 1820s – or thereabouts.

This article is part of our series on magnetism and electromagnetism. Because this is the fundamental phenomenon on which power transformers are based. Do you remember what electromagnetism is all about? If not, before you read on, check out our article on the science of electromagnetism.

If yes, then let’s crack on. Let’s talk about the power transformer – one of the most underrated objects we have.

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We wouldn't be able to transfer electricity without electromagnetism.

What is a Transformer?

So, the most important question: what actually is a transformer?

Simply put, an electrical transformer is a device that transfers electrical energy from one circuit to another. The cool thing – and the crucial thing for industry and the like – is that it does this without the need for any sort of metal connection between the two circuits.

That’s it; that’s all it does. Yet, the opportunities that these little devices provide are absolutely huge – as you’ll see in more detail below. Because it is in the nature of power grids and electrical circuits that connections between different circuits are crucial.

And this is particularly true when we are talking about circuits that require different voltages. And this is the second major thing that transformers do: they allow the transfer of power from a circuit of high voltage to one of low voltage or medium voltage.

This particular fact is really important – as you will see.

Power Distribution and Power Transfer.

But let’s take the role of transformers in power distribution first.

Pretty much all electrical power in the world passes through a transformer at at least one point in its life cycle. It is incredibly likely, in fact, that it passes through several. Only the smallest fraction of electrical energy is produced by on-site generators – and so doesn’t need to be transferred.

And so, transformers play a role in all the energy that comes into the conventional home.

Electricity distribution happens on an absolutely massive scale – crossing countries if not entire continents. Considering that the electrical current has such a long way to travel from the producer to the consumer, transformers are often used to break up the circuit into smaller parts. This allows greater stability in the line – and makes it easier to isolate issues.

Step Up and Step Down Transformers.

The most common use of transformers is in their particular roles as a step-down or step-up transformer. These underpin the functioning of the whole electrical grid – and permit the arrival of any electrical energy into your home.

Voltage vs Current.

This is because the electrical grid works through transmitting electrical currents of extremely high voltages.

Things like the National Grid, the electrical transmission network in the UK, can’t really use high currents. Generally speaking, the higher the current, the less efficient the transmission is. With higher currents, more heat is produced – and more energy is lost as it is released through the wire.

Current is the rate of flow of electrical charge. So, the higher the current, the quicker the electricity passes through the wire. And whilst this is all well and good, so much of the electrical energy is wasted if you transfer it over long distances.

Voltage, on the other hand – or EMF as it is sometimes known, electromotive force – is the potential difference between two different points in a wire. This is the electric pressure that allows the current to flow. In other words, it is the amount of energy that is required to transfer current along a wire.

These things are all using magnetic fields.

Transforming Voltages.

So, electrical grids use incredibly high voltages – rather than high currents. But there is an obvious problem with this. Whilst high voltage electricity is much easier and more efficient to be transferred, it is much more dangerous to actually use. Having incredibly high voltages in all our plugs would not be very clever.

And so, the grid uses transformers to ‘step-up’ the voltage of the electricity before it is to be transmitted and to ‘step it down’ again afterwards. Before it can be distributed on a local level – and before it reaches anyone’s home – the voltages need to be hugely reduced, as the voltages in national wires are thousands of times higher than those that your laptop or your kettle could handle.

This is happening with all of our electrical energy. So, you can see how important these transformers are for our lives.

How Do Transformers Work?

Now you know what transformers do. But how do they do what they do? This is the question to which we need to give an answer now. And you’ll find that that answer is linked entirely to the force known as electromagnetism.

Electromagnetism is the interface or combination of electric current and magnetism; these two things are two sides of the same coin. And transformers work by exploiting this relationship.

Transformers are really quite simple devices. In their simplest forms, they are two coils of wire around a ferromagnetic core. Imagine this to be a ring of iron, on the opposite sides of which are two windings of copper wire.

A current passes through one, and into what we’ll call the primary winding. As the result of the electric charge’s magnetic field, changes in the magnetic flux of the iron core will electrify the secondary winding on the other side. This, quite simply, is the basis of how the ideal transformer would work – through this process of what we would call electromagnetic induction.

Faraday’s law – named after the man who discovered electromagnetic induction, as you’ll see below – states that you only need to change the number of coils on the secondary coil and you change the voltage that appears in the second circuit.

Faraday and Magnetic Flux.

It was Michael Faraday that discovered these principles of electromagnetic induction that have become central to the technology of the transformer.

He built himself a little transformer exactly as we just described it above. And, linking one side up to a battery and the other side up to a galvanometer, he noticed that the electrical charge was only present in the secondary wire when – and only when – he connected and then disconnected the battery.

This was the essential part of his discovery. When the electrical current was stable in the first wire, no electricity was observed in the second. What was required was the change in the electrical charge. It was this change that effected the change in magnetic flux in the iron core – which permitted the transmission of electricity.

The Importance of Alternating Current.

This discovery informs the way that transformers work today. As they only work with alternating current – as opposed to direct current.

Whereas direct current is a stable current that only travels in one direction, alternating current – or AC – continually changes direction. This produces the change to the magnetic flux that permits the transfer of electrical current across the transformer – or, in other words, that permits the induction of electricity in the secondary wire.

Without this variability of the magnetic field in the transformer, there could not be any transfer of electricity at all.

magnetism compass
Compasses use the same physical principle as transformers.

The Importance of Electromagnetism.

Michael Faraday made this discovery back in the 1830s. And, although there have been attempts to make the process simply more efficient, the fundamental principles of the transformer have not changed one bit – and nor will they ever.

This is why the transformer testifies to the fact that electromagnetism is one of the most important discoveries in the history of our world.

So, you better make sure you learn it.

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