Science!
Well, today I did OK on the not reading social media before getting up. But not too good on the getting up early. Which admittedly is my own fault for reading a book until nearly 3am. Haven't done that in a while. It was a re-read too, The Enigma Score by Tepper. Now Tepper is an author that I can take or leave. Some, like this one, I liked a lot. Others have done nothing at all for me. So I'm not generally inclined to just pick up one of hers. This is my second copy, thanks to 
fred_mouse who found a copy when over in the UK. I know I had one before but I don't know if I loaned it or what, but it hasn't been seen in ages. So was rather glad to get it back. Some interesting world building, both for the mobile sentient species, and the immobile (mostly) ones. It even ties into my work slightly with the section at the end explaining about crystal defects. But it had been a long time between reads and I was up late to start with and whoops.
Still, I got up eventually and in to work, and prepared for my lecture that I was giving in the afternoon. Charged particles in magnetic fields, and applications thereof. You can do some nifty things with combinations of magnetic and electric fields. Magnetic fields cause moving charged particles to change direction, basically it causes an acceleration towards the centre of circle, a bit like how a planet orbits a star or a moon a planet, except that it's not caused by anything in the middle of the circle but by the magnetic field perpendicular to the movement of the particle. Since the force that acts on it is perpendicular to both the magnetic field and to the velocity of the particle. And the way it bends it affects its direction but not its speed. So the magnitude of the velocity stays the same, but the direction keeps changing and it goes round and round in a circle. So far, so good. The radius of the circle depends on the momentum of the particle (the bigger the momentum, the bigger the circle) and the charge and magnetic field strength, the bigger they are, the smaller the circle. So you can adjust things somewhat with the magnetic field to affect the radius of the circle. If you can control that. Which is relatively easy to do with electromagnets.
All of which is nice, but the real trick is that you can also apply an electric field, at right angles to the magnetic field and the initial velocity of the incoming particle. Get it the right way round, and the particle will experience a force from the magnetic field in one direction, and a force from the electric field in the opposite direction, and if you get the magnitudes of the fields right then instead of being bent, the particle will go straight. Now what the electric and magnetic fields need to be for that to happen depends on the velocity, or at least the speed of the particle. (v=E/B - hope equations not scaring anyone away). Which means that if you want to make particles of only a particular speed get through a slit, you can do that by having your electric field and magnetic field of the right strengths, any particles that come with a different speed get bent and go splat on whatever you have in the way to stop particles that don't go straight (and believe me, I'd much prefer to not go down that wording path but it's late and I can't think of better ones).
Now the nice thing about that is that if a particle has a particular speed, and you know what mass it is, then you can work out what energy it has. If you don't know what mass it has, you can stick another magnetic field on the other side of the slit and work out what radius it gets, which will give you at minimum the mass/charge ratio, or if you actually know the charge, will give you the mass specifically. All of which of course is very nice and useful for making such things as mass spectrometers. Then finished off with some theory of the cyclotron. Which I understand a lot better now than in my undergraduate days.
I did manage to do my dishes, and my new 5 books shelving habit, so that's good. I helped several students out with questions, including one fairly lengthy phone conversation, attempting to debug (not sure if that's the word) determine what was wrong with an electronic DC circuit on a breadboard that's not even remotely near here. Still, with a couple of pictures so I can see what they were looking at and some step by step diagnostics we did get it working, so yay there!
And I did the gym, while virtuously reading up on tomorrow's lecture. So I can go back to getting my marking done. I think Wednesday doesn't have any contact hours as such so that will be a definite marking day.
And now since I don't want to repeat the 3am debacle it's time to finish up and get to sleep.
It's possible I'm boring a lot of people with this, and the last couple have been friends locked, (and I did put in a cut usually) but if people would prefer not to read all my daily unwinding let me know. I can set up a filter, though since it's usually not going to contain any TMI stuff most of the time I think people just skim past the cuts.
Originally posted at http://ariaflame.dreamwidth.org/89389.html where you may comment if you wish. There are currently
comments on the original post.
fred_mouse who found a copy when over in the UK. I know I had one before but I don't know if I loaned it or what, but it hasn't been seen in ages. So was rather glad to get it back. Some interesting world building, both for the mobile sentient species, and the immobile (mostly) ones. It even ties into my work slightly with the section at the end explaining about crystal defects. But it had been a long time between reads and I was up late to start with and whoops.
Still, I got up eventually and in to work, and prepared for my lecture that I was giving in the afternoon. Charged particles in magnetic fields, and applications thereof. You can do some nifty things with combinations of magnetic and electric fields. Magnetic fields cause moving charged particles to change direction, basically it causes an acceleration towards the centre of circle, a bit like how a planet orbits a star or a moon a planet, except that it's not caused by anything in the middle of the circle but by the magnetic field perpendicular to the movement of the particle. Since the force that acts on it is perpendicular to both the magnetic field and to the velocity of the particle. And the way it bends it affects its direction but not its speed. So the magnitude of the velocity stays the same, but the direction keeps changing and it goes round and round in a circle. So far, so good. The radius of the circle depends on the momentum of the particle (the bigger the momentum, the bigger the circle) and the charge and magnetic field strength, the bigger they are, the smaller the circle. So you can adjust things somewhat with the magnetic field to affect the radius of the circle. If you can control that. Which is relatively easy to do with electromagnets.
All of which is nice, but the real trick is that you can also apply an electric field, at right angles to the magnetic field and the initial velocity of the incoming particle. Get it the right way round, and the particle will experience a force from the magnetic field in one direction, and a force from the electric field in the opposite direction, and if you get the magnitudes of the fields right then instead of being bent, the particle will go straight. Now what the electric and magnetic fields need to be for that to happen depends on the velocity, or at least the speed of the particle. (v=E/B - hope equations not scaring anyone away). Which means that if you want to make particles of only a particular speed get through a slit, you can do that by having your electric field and magnetic field of the right strengths, any particles that come with a different speed get bent and go splat on whatever you have in the way to stop particles that don't go straight (and believe me, I'd much prefer to not go down that wording path but it's late and I can't think of better ones).
Now the nice thing about that is that if a particle has a particular speed, and you know what mass it is, then you can work out what energy it has. If you don't know what mass it has, you can stick another magnetic field on the other side of the slit and work out what radius it gets, which will give you at minimum the mass/charge ratio, or if you actually know the charge, will give you the mass specifically. All of which of course is very nice and useful for making such things as mass spectrometers. Then finished off with some theory of the cyclotron. Which I understand a lot better now than in my undergraduate days.
I did manage to do my dishes, and my new 5 books shelving habit, so that's good. I helped several students out with questions, including one fairly lengthy phone conversation, attempting to debug (not sure if that's the word) determine what was wrong with an electronic DC circuit on a breadboard that's not even remotely near here. Still, with a couple of pictures so I can see what they were looking at and some step by step diagnostics we did get it working, so yay there!
And I did the gym, while virtuously reading up on tomorrow's lecture. So I can go back to getting my marking done. I think Wednesday doesn't have any contact hours as such so that will be a definite marking day.
And now since I don't want to repeat the 3am debacle it's time to finish up and get to sleep.
It's possible I'm boring a lot of people with this, and the last couple have been friends locked, (and I did put in a cut usually) but if people would prefer not to read all my daily unwinding let me know. I can set up a filter, though since it's usually not going to contain any TMI stuff most of the time I think people just skim past the cuts.
Originally posted at http://ariaflame.dreamwidth.org/89389.html where you may comment if you wish. There are currently
comments on the original post.