You've likely heard of the word "current" being associated with electricity, and with good reason!
Electricity is a phenomenon that's produced when charged particles, like electrons, move through a medium like copper wiring.
See, charge is a property of a subatomic particle, just like mass is, and just like how mass can have a massive impact on the way particles interact with the world, so can charge.
In fact, when charges move, they create a current of energy, which produces the phenomena that we call electricity and magnetism - they're both inherently connected, although you might
not assume so if you hadn't been told as such before.
Every charged particle exhibits an electric field, but only moving charges can exhibit a magnetic field - charged particles that are stationary do not produce magnetic fields.
I'm not going to bother with the ins-and-outs of electricity, since this article is specifically about super-conduction, but suffice to say that when charged particles like electrons move, they create a current, which in turn realises electricity.
And how do you get electrons to move?
By applying a Voltage, but the details aren't all that relevant to this article, so we'll move swiftly on!
The trouble is though, as electrons move through mediums like gases, they get repeatedly smashed into by the gas particles as gas particles move around their "container" at high speed...
You'll hear the word "container" a lot in physics, but just know that it's simply a general word to describe the region that a particle moves across.
Therefore, you've got a hard job conducting a current through gases, although it's not impossible, as you've may have just worked out if thunder and lightning came to mind (specifically lightning).
If you move down to liquids, of which particles slowly wobble and very gently transpose (a fancy word for "move") in groups, then you find that electrons have a much easier job flowing through and hence creating current.
There's essentially less chance of electrons bumping into liquid particles, meaning they're far more likely to be able to flow through the material and hence create a current.
Remember, a current just describes the flow of charged particles like electrons.
Finally, you can take this a step further and say that with solids, where particles have no transpositional velocity and merely vibrate back and fourth, electrons have a very easy job flowing through and creating a current.
In fact, metals in particular, which you probably know are exceptionally good at conducting electricity, even have an atomic structure such that lends itself very well to the flow of electrons.
Metals have a molecular structure whereby even some of their own electrons can move from atom to atom, which we refer to as delocalised electrons, as they're no longer considered local to any particular atom.
That's why metals are such great conductors, but what do I mean by super-conduction?
Even though solids like metals are of the lowest energy state, they still have some energy, which partly takes the form of kinetic energy, giving them their vibrational velocities. The lower the energy that they have, the smaller the distance of which they vibrate, or oscillate back and fourth over.
Why is this significant?
Well, electrons need as much space as possible to avoid collisions, so the smaller the distance of which the particles vibrate over, the better that material will conduct electricity, as the collisions with electrons become less frequent.
Perhaps it would best if you checked out my other article on states of matter here if you're struggling with the differences between solids, liquids and gases.
All you need to know though is that the particles in a gas have lots of energy and move around at really high speeds, the particles of a solid do not move at all, although they do vibrate back and fourth over small distances, and particles of a liquid are somewhere in between!
Maybe you can see where I'm going with this, but when you cool metals down to insanely low temperatures, the amount of energy that the particles have is so little that they barely vibrate at all (although, importantly, they still have some energy).
At these temperatures (and we're talking -200 degrees Celsius and below!), electrons are able to easily and rapidly move through metals, which means that the current they create can be huge.
The lower the temperature, the "better" the current, but it's important to note that the lowest theorised temperature is -273 (to 3 s.f) degrees Celsius, or Absolute Zero as it's referred to as, and it can never be achieved.
If you're interested in learning why, then I'd suggest reading this article.
More importantly for us though, this rapid movement of charges means that a huge magnetic field can be induced, and one with incredible strength.
This level of conduction is known as super-conduction, and it's what MRI machines rely on!
Inside of those massive tubes, as shown in the picture above, is liquid helium, and helium boils (changes from liquid to gas) very easily.
In order for helium to be maintained in a liquid state, it must be cooled to a beyond freezing -270 degrees Celsius!
Quick tip - the temperature of an object is a measure of the energy of the particles that make up that object, and the higher the energy, the higher the temperature.
That's extremely close to the coldest temperature in theory - Absolute Zero, although again, it's impossible to ever get to this temperature for reasons that I discuss in the other article (you can click here).
At that temperature, super-conduction can occur which creates a magnetic field powerful enough to allow for imaging of the human body - If you've ever had the misfortune of being in one, you'll know that they tell you to remove anything metal from your person, since it will be rapidly stripped away from you when the magnet turns on!
MRI stands for Magnetic Resonance Imaging, and if you're interested in the physics behind how and why they actually work, then I'd recommend reading this article!
Besides the now obvious that they involve super-conduction :)
Thanks for reading!