Paramagnetism and Diamagnetism

You might not think of water is being magnetic. But it is. And so are graphite, aluminum and glass. This is a new and different category of magnetism called either para of dia magnetism and it is different from the magnetism that you're used to. You're probably already familiar with ferromagnetism. Ferro means iron. An unmagnetized piece of iron or nickel or cobalt becomes a magnet in the presence of a magnetic field. The effect is strong and lasts even after the magnet is removed. Paramagnetism is a similar effect except that it's much weaker and temporary. Aluminum is a good example of a paramagnet and so is oxygen which is attracted to magnets. Here I have a few milliliters of liquid oxygen which sticks to the magnet. I'll explain why later. Gadolinium oxide in cupric sulfate are good examples of paramagnetic substances. Cupric sulfate is as salt that can be picked up by a magnet. Diamagnetic materials are exactly the opposite of paramagnetic. They're always repulsed They would rather die than be a magnetic field. An important example of a diamagnetic material is graphite. The specially made pyrolytic graphite is repelled by a magnetic field. Don't be confused this is not static electricity or eddy currents. Graphite is repelled by a magnet always, both by the North and South end. Pyrolytic graphite is a grown crystal of flat carbon layers which maximizes the diamagnetic affect. Of course the best diamagnets are superconductors which at low temperatures provide exact opposite repulsion to whatever magnetic field is present. When they're chilled they are perfect diamagnets. The most famous and powerful diamagnetic is bismouth element number 83 on the periodic table. The bismouth powered boat sails toward the weaker magnetic fields. One way to check whether an object is diamagnetic or paramagnetic is to see how it aligns itself in a magnetic field. Diamagnetic objects like glass will rotate to avoid magnets. Here we see that the glass is diamagnetic because it twists to get to the weaker magnetic field. But aluminum rotates into the field typical of a parallel, para magnet. On the periodic table we see that aluminum has three valence electrons. So what does it take to understand what it means for something to be a para magnet or a diamagnet? You have to know what the electrons are doing. Consider for example aluminum. We see from the periodic table that aluminum has theree valence electrons. That is 2s and 1p. Now it's that unpaired electron that makes it a paramagnet. This unpaired electron enables it to become magnetized. And it's that unpaired electron that is free to be magnetized and attracted by the magnet. But what about a diamagnet? like water? Yes the water molecule it has all of its electrons paired. It will not be magnetized. In fact water is repelled by magnetic field. The electrons come to lower energy as they are moved away from the magnet. In conclusion when something is a paragmagnet or a diamagnet it tells you what its electrons are doing. In the case that the paramagnet it has at least one unpaired electron. In the case of a diamagnet it has mostly paired electrons.

Channel: uclaphysicsvideo

Views: 932,641

Rating: 4.9267259 out of 5

Keywords: magnetism, paramagnetism

Id: u36QpPvEh2c

Length: 4min 31sec (271 seconds)

Published: Fri Nov 08 2013

Reddit Comments

[u/glvelaz1]

Wow I really like his way of teaching this. Very easy to understand

[u/[deleted]]

deleted ^{What is this?}

[u/benthicdweller]

His latest video is 2years ago tho.

[u/stupidreddithandle91]

His explanation of paired electrons did not seem to me to explain the distinction between paramagnetism and diamagnetism. Since I already understand what is meant by “paired” I understood why an atom with an unpaired electron would have a much greater magnetic moment. So that explains why something with unpaired electrons would be paramagnetic and also why something with only paired electrons would not be paramagnetic. But that doesn’t explain why it should be diamagnetic. I take it to mean that all materials have weak diamagnetism, but in paramagnetic materials, paramagnetism dominates. But it wasn’t clear from the explanation. So why would something with paired electrons be at a lower energy in a weaker B field?

[u/ProfStretchy]

Great video.

[u/Quasar_Optics]

Great job would love to see an entire material science series on types of interesting material properties!

[u/paiute]

You had all day to write on the board. Get it straight.

[u/CoraLRock]

this is the most usefull video work i have ever seen about em ty

[u/stumpdawg]

Fuckin magnets. how do they work?

seriously though, this was interesting.