 Check out this experiment. I found on YouTube by Irvin the Gupta There is a beaker attached to a rubber making it float on a type of water and the beaker contains water in it and Somebody's bringing a strong magnet close to it and see what happens You see that the water ends up repelling by the magnet repelled by the magnet. Can you see that? What? Why why is water repelling a magnet? How does that make any sense? Okay, let me show you another another one. This is a demo by the famous professor Walter Lewin at MIT He's pouring liquid oxygen into an electromagnet. See what happens. There we go Look at what you see you see that liquid oxygen sticks sticks to the magnet meaning it gets attracted to magnet What's going on? Why are these things attracted and repelled to magnet? This shouldn't be isn't it? Well, it turns out that most materials are actually either slightly attracted or repelled by magnets So with careful experiments you can actually see that But what's mind-boggling to me is whether it's attracted or repelled depends on and get this it depends on Whether the atoms of that element have paired electrons or unpaired electrons But why how does that decide whether something is attracted or repelled by a magnet? Well, let's find out We've already seen that atoms tend to have magnetic moments because of electrons going around forming current loops current loops give magnetic Moments which basically means they act like tiny tiny magnets, but most atoms have more than one electron and The electrons tend to pair up now whenever electrons pair up You can imagine that the two the two form current loops in the opposite direction giving the net current zero So their magnetic moments cancel out So this means if you have atoms where all electrons are paired up and their magnetic moments cancel out They do not behave these atoms do not behave like tiny magnets on the other hand If you have at least if the atoms have at least one unpaired electron Then they will generate some magnetic moment and these atoms do behave like tiny magnets Now let's see what happens when you bring a magnet close to them. So let's start with the atoms that are completely paired up What would happen if I were to bring a giant bar magnet close to it? My first thoughts are these atoms do not behave like tiny magnets, right? And so they should be completely unaffected by magnetic fields. So nothing should happen, right? Well, don't forget about Electromagnetic induction and I might be like what are you talking about when I brought the magnet close to this The magnetic flux through these loop Changed and we know from Faraday's law that now there will be an emf induced in these current loops Which tells it tends to oppose that change lenses law and so there will be an emf induced that tends to oppose the field Which means the emf will be induced in this direction the blue currents direction So what that means is that induced emf strengthens in this current So I'm going to show this current little bigger that this current becomes stronger because of the induced emf But this current becomes a little weaker because the induced emf is in the opposite direction to this current And so the current now becomes a little weaker and as a result look they are no longer going to cancel each other out There's going to be a slight difference that this magnetic moment is slightly higher than this one and So there is a small magnetic moment induced and starts behaving like a tiny magnet And so look due to lenses law the atom starts to behave like a tiny magnet and look at how it's oriented in the opposite direction So is it going to attract or repel? It's going to start repelling it Same thing is happening in the water water molecules are all paired up But when you bring a magnet close to it due to induction they behave like tiny magnets and as a result the whole water gets slightly magnetized in the opposite direction and ends up repelling the magnet This phenomena where atoms starts repelling the magnetic field due to induction is what we call dia magnetism and such materials like water are called dia magnets and The examples include water of course and a lot of organic substances like you me would all of us are dia magnetic living beings Are all dia magnetic and there are some metals as well Which will get back to towards the end of the video and although dia magnetism is a very very weak property Which is why you should do very careful experiments to see that if the external field is strong enough The force the repulsion could be strong enough and you can use that to levitate things And so for example if you bring this bar magnet from a giant magnet from the bottom and put a frog on top of it It has been done the frogs tend to levitate because of the dia magnetism the repulsion can be stronger than gravity You can you can check out some videos of frog levitating by magnets pretty cool But now here's my question for you. What would happen if I were to take that magnet away? Do you think that this magnetized water would stay magnetized now or something else would something would happen to them Can you pause and think about it? Okay, again electromagnetic induction will take place but this time because the magnetic flux is decreasing You'll try to increase it from Lenz's law So there'll be induction happening in the opposite direction. This will completely kill this current and the water would lose its magnetism So diamagnetism is not only weak, but it's also a very temporary phenomena Okay, now let's consider materials which whose atoms have these permanent Dipoles they do behave like tiny magnets Oxygen is an example so an immediate question to me is why does an oxygen behave like a magnet because the atoms of oxygen Do behave like magnet, right? Well, if you could look at all the atoms Inside say oxygen what we'll find is that there the their magnets these magnets are all randomly oriented And so although each atoms do at atoms do behave like tiny magnet as a whole all their magnetism gets completely killed Because of the random orientation and so oxygen as a whole still doesn't behave like a magnet But now what do you think will happen if we bring it close to a magnetic field? Well, the magnet starts putting a force on these tiny magnets if you look over here the North Pole gets repelled The South Pole gets attracted and as a result it'll turn So all these tiny magnets tend to turn and get aligned in the direction of the magnetic field and Because of this it's no longer random pretty much this side is now behaving like a North This side is behaving like South and now the oxygen has been slightly Magnetized this material is slightly magnetized, but look in what direction it's magnetized. This is South means it gets attracted and this phenomena where materials attract magnets is what we call para magnetism para magnetism You might see that they're not completely aligned mainly because there's a lot of thermal agitation these things are all vibrating So they're somewhat aligned which means paramagnetism is also very very weak and again We need careful experiments for this and such materials that get weakly attracted by magnets are called para Magnets and I'll put a star over here mainly because not all materials that have unfair electrons behave like para magnets We'll get back to that towards the end of the video But anyways the examples include of course oxygen and now you know why oxygen got stuck in that magnet mainly because it's a Paramagnet, but other examples include aluminum calcium, and I'm sure there are other examples out there And again the same question over here. What would happen if I were to get rid of that magnet would oxygen stay magnetized? Well, now there's no reason for them to stay magnetized because remember all these atoms are jiggling and vibrating randomly And so what will happen is they will go back to how they were before and it will lose its magnetism So again paramagnetism is a very weak and it's also a temporary phenomena So now before we move on to that last part where I put the a stick over here Can you pause and differentiate between diamagnetism and paramagnetism see what differences and similarities do you see? All right, so first of all this repels and this attracts Secondly this works on paired electrons. This is on unpaired electrons here We have temporary dipoles induced in the opposite direction once you get rid of the magnet the dipoles are gone Here you have permanent dipoles that are turning due to the magnetic field Another important question is how does it how does temperature effect affect them? So let's look at paramagnetism first What do you think would happen if I were to lower the temperature make reduce the temperature? Do you think the paramagnetism would get stronger weaker or do you think it wouldn't change? Can you pause and think about it? Okay, we saw that paramagnetism happens due to alignment the more alignment the more paramagnetism, right? But remember the enemy of the alignment is the thermal vibrations more thermal vibrations harder It is to align so at higher temperatures more thermal vibrations higher harder it is to align less paramagnetism and that's why when you lower the temperature you get higher paramagnetism in fact That's the reason why liquid oxygen is highly paramagnetic Compared to gas oxygen because it has a much lower temperature and of course it's also because liquid oxygen has more density more atoms per cubic meter more attraction But anyways, what about diamagnetism? How do you think it changes with temperature? Well diamagnetism does not depend upon the vibrations of the atom at all It is due to the currents induced, right? The currents induced does not does does not depend on whether the atoms are vibrating or not vibrating And therefore diamagnetism is pretty much independent of temperature. So that's another big difference that you see What similarities do you see? Well, they're both pretty much weak and they're temporary phenomena and that's where Ferromagnetism is different ferromagnetism you can retain the magnetism Even after you remove the magnets, but they're so cool. There is a video of their own So let's let's not talk more about ferromagnets here Finally, I said that not all materials whose atoms have unpaired electrons behave like paramagnets and I'll give you examples Copper gold silver. They all have an unpaired electron. They do not behave like paramagnets They behave like diamagnets. Why do you think that happens? Can you pause and you know make come up with a theory for that? Okay, here's a big question for you Whatever we saw over here the whole electromagnetic induction causing diamagnetism shouldn't that happen here as well I mean even this also contains paired electrons inside, right? All atoms have some or the other paired electrons inner electrons So shouldn't they undergo diamagnetism same phenomena, right? They do Diamagnetism is a universal phenomena. You can find that in every single material Whether it is iron or oxygen or aluminum doesn't matter no differentiation Every material have some or the other degrees of diamagnetism So even in these material even inside oxygen you have diamagnetism happening as well Which tries to repel the the external magnet and so eventually what ends up happening depends upon which is stronger Now in most cases paramagnetism is stronger than diamagnetism and that's why they end up becoming paramagnets So all these examples are the ones where paramagnetism is stronger. So let me write that down So the astragore here is this will only work if the paramagnetic phenomena is larger than the diamagnetism because diamagnetism is there everywhere But in some cases Diamagnetism can be stronger than paramagnetism and in these cases your materials ends up becoming diamagnetic and the examples of copper gold Aluminium these are all examples where diamagnetism is becoming stronger. Sorry Diamagnetism is stronger and that's why they behave like diamagnets So long story short all material tend to repel magnets, which is then in this phenomena is called diamagnetism This happens due to electromagnetic induction and lenses law But in materials that have permanent dipole moment There is an additional phenomena called paramagnetism because of which it tends to get attracted by the magnets So materials in which paramagnetism is stronger than diamagnetism We call them as paramagnets and they end up getting attracted by the magnets and this is temperature dependent And in materials in which you either don't have unpaired electrons or in which paramagnetism is stronger than diamagnetism They eventually end up getting repelled by magnets and we call those diamagnets