Magnets are one of the most common tools in our day to day lives, popping up in all sorts of contexts and places. Look at the door of your fridge – which is held tight by magnetism. Think about your headphones or computer speakers; magnets power them. Or play with your parents’ car window; that too is made possible by magnetic materials.
Magnets are, quite literally, everywhere. Electricity and magnetism – and the science behind the magnetic field – are some of the most useful scientific tools we have. So much stuff would just not work if we didn’t have them.
Yet, given the ubiquity of magnetic material and magnetic tools, we sort of take this phenomenon for granted. But if you stop and think about it, isn’t magnetism amazing? Isn’t it incredible that a piece of metal can move another through some invisible force? Don’t you think that the science of this strange process is actually pretty cool?
No? Well, maybe that’s because you don’t know enough about it. So, with the intention of persuading you that magnetic force is actually one of the most interesting things in nature, let’s take a look at what it is all about.
We’d be surprised if you didn’t agree by the end of this article. You can check out our full guide to magnetism and electromagnetism too!
What is Magnetism Exactly?
Magnetism is the force by which magnetic materials attract and reject other magnetic materials. This is the most common way in which you see magnetism in action in everyday life, when bits of metal are pulled towards other bits of metal.
This, incidentally, is what makes magnets so interesting – and so useful in day-to-day life. Magnetic force is a non-contact force, meaning that magnetic materials don’t need to be touching for their effect to be felt.
Yet, this is not just magic – although it may once upon a time have been believed to be such. Rather, the forces that these materials enact are the result of a process that happens at a level too small for us to see with our eyes. At this level, everything is in motion.
And what creates the force that we witness is the result of two phenomena at that level. The first being the ‘magnetic moment’ of a given element and its particles – and the other being an electric current.
Magnetic Moments and Electrons.
What is happening at a much smaller level is all about electrons, one of the subatomic parts of a material.
These electrons move, or rotate, around the nucleus of the atom. And each one has a different charge – generally either positive or negative. Normally, the electric charge or spins of these electrons are balanced – meaning that the number of positive electrons is equal to the number of negative electrons.
Nature tends to like stability and stasis and, in this context, this means that nonmagnetic materials are the norm, due to the fact that with the equality of positive and negative electrons, the magnetic moment of these electrons is cancelled out. This is helpful as, otherwise, everything in the universe might be magnetic – which wouldn’t be super convenient.
Sometimes, the electrons in a material aren’t balanced – this is true. However, more often than not in such cases, their magnetic charge is not aligned – something that is a prerequisite for magnetism proper.
Magnetism in the way that we recognise – with the two magnetic poles of a magnet – occurs when the electrons’ magnetic moments are all aligned, i.e. pointing in the same direction. Only at this point will a material produce a magnetic field strong enough to be relevant.
Find HSC Physics tutor on Superprof.
Electricity and Magnetism.
As we said, there are two sources of magnetism. The first is the magnetic moment of the given electrons and their alignment. The second is an electric current.
Electric currents produce magnetism because electricity is the flowing of electrons through a material. With this, you have a phenomenon in which all the electrons become necessarily aligned through their motion – and this motion gives the electric wire a positive charge and a negative charge.
You’ll have probably heard of an electromagnet – or of electromagnetism in general. These are super-strong magnets that are powered by electricity. Along with the majority of things that are powered by electricity, you can turn these on and off too – which makes them quite convenient for industry.
If you take a magnetic substance and wrap a coil of wire around it – with an electric charge passing through it – you will find that the resulting magnet is really very strong indeed. The whole coil becomes magnetized in this way, with the electrons from the wire producing a magnetic field that attracts into the centre of the coil.
As soon as you switch off the electricity, the coil is no longer magnetic.
This is a crucial part of electromagnetism.
What is a Magnetic Field?
Magnets attract and repel other things that are susceptible to the force of magnetism. We know this.
Yet, the important thing is what happens between the two materials that are magnetic. This is the magnetic field – an invisible field of force which is essentially the arrangement of the electrons in the surrounding area.
You’ll have seen the diagrams of magnetic fields before. And what you’ll recognise is the dipolar nature of magnets – the fact that magnets have both a north pole and a south pole – as well as the magnetic field lines which we tend to draw between the dipoles.
These lines represent the magnetic flux that emerge from the north pole and enter the south. The closer together the lines, the stronger the magnetization. These lines never ever cross, by the way.
One of the best ways to see a magnetic field for real is through the use of iron filings.
Get yourself a bar magnet and a handful of teeny-tiny bits of metal – iron filings, essentially the dust of iron.
Drop the iron onto the magnet and watch the magnetic field appear, with all the different lines of force included. It’s quite impressive, actually.
Search for physics tutor on Superprof.
Different Types of Magnets – and Different Types of Magnetism.
You probably have the impression already that not all magnets are the same. Given that we know that there is such a thing as electromagnetic force, as well as ‘normal’ magnets, we can pretty much assume that there are more types of magnet too. We’ve already mentioned bar magnets, for example.
Scientists love to characterise things – and you need to know the categories that they create.
Let’s start with diamagnetism. This is the type of magnetism which everything has all of the time. However, it is not particularly ‘magnetic’ in the sense with which we are conventionally familiar.
Rather, in a material that is ‘diamagnetic’, there are no unpaired electrons at all. And, in the presence of paramagnetic or ferromagnetic substances, the diagmagnetism is overwhelmed.
Paramagnetic materials are those that are weakly attracted to any magnetic field to which they are exposed. The majority of chemical compounds are paramagnetic, because they usually have electrons that are not paired (see above). This means that even elements like oxygen are actually paramagnetic – something of which maybe most people are unaware.
In paramagnetic substances, the unpaired electrons align to the magnetic field, giving the substance an overall charge.
Ferromagnetic materials are those that we conventionally recognise as magnetic.
These materials have unpaired electrons too. However, unlike in paramagnetic materials, the electrons in ferromagnetic materials tend to line up spontaneously. This means that they don’t need an external magnetic field in order to become magnetic.
These materials are the commonly magnetic ones – such as iron (hence the name ‘ferro’), nickel, and cobalt.
Find Physics tutors Melbourne on Superprof.
Temporary Magnets and Permanent Magnets.
These two terms – temporary and permanents magnets – are fairly common in conversations about magnetism. And the difference is probably fairly obvious.
Permanent magnets are those that are ferromagnetic. These retain their magnetic potential even after they are not in the presence of an external magnetic field.
Temporary magnets are those paramagnetic substances that require an external magnetic force. These things are like paperclips – objects that react to magnetism but are not themselves magnetic.
By the way, heating a ferromagnetic substance messes with its magnetic potential. The energy of heat creates much greater atomic volatility – meaning that the electrons cannot remain aligned.
Find out about transformers, one of the most important magnetic technologies!
Is the Earth Magnetic?
You know that the Earth has a magnetic field, right? That’s the reason why we give magnets the characteristics of having a ‘north’ pole and a ‘south’ one.
The whole of the globe is magnetic – which is the reason why compasses work. If you were to pick a handful of mud, it wouldn’t be magnetic, but the size of the earth produces the biggest magnetic field on the planet.
Why does it do this? No-one is quite sure. However, scientists think that it is because of convection currents in the Earth’s core – which are primarily made of iron and nickel. And it's that that produces the northern lights.
Ever heard of electromagnetic induction? Find out about it here.
The platform that connects tutors and students