WHAT HE SAID WAS I can actually show you that with a real charged beam. So this is an evacuated tube and it puts a big negative potential on this electrode. So high that it actually boils, electrons come off the electrode and makes just a beam of electrons. It also has some ionized, a little bit of a background gas that ionizes to keep everything stable and doesn't charge up too much. But mostly you have electrons flying off this electrode and most of them go straight to this metal plate and that's the end of the story. But there's a little slit in the plate. So some of them get through and make a beam that keeps going. So you've got a beam of electrons and this little plate is tilted a little bit so they slowly along this direction they crash into the plate. The plate has a phosphor on it so it lights up when they crash into the plate. So when I turn it on, there you can see the beam. That's a beam of electrons flying through the tube. So what we're going to do is bring a magnet and see what it does to the beam of electrons because remember this bar magnet, the field lines go from the north pole, the red is the north pole to the south pole. So if we just think about the poles or the field right at the ends because we're going to use the ends, it will be this way near the north and it will be pointing in in the south. So I will bring the north pole pointing at me at the beam and let's see what that will be. We have the beam going this way and I'm going to bring this pointing in so we're going to have a B field like this. So V cross B also the same as this. It should be up. So let's see what happens. There's our beam and I bring in this magnet. There's the deflection we hope for but it's down and it's down and why is it down? It's down because they're electrons. Q in this case equals negative E. The charge is negative. When the charge is negative the force magnitude is negative which means it goes the opposite direction. So right hand rule says it's up for positive but the force is down. for an electron. So it did deflect the right way. It deflected down. We can also check. We can take and aim the south pole at the beam. So here we go. Bring in the south pole. And there it goes. It deflects up, just like you'd expect. Because when you're bringing the south pole, the magnetic field is pointing the opposite direction. Now I'm bringing in a field that's pointing away from the beam. So it would seem that the charged particle beam really is deflected the direction that you would expect.
The more interesting questions is, does a beam of electrons create a magnetic field? The relativistic explanations usually given for magnetic effect are very confusing.
@Physierge 1: if a moving electron creates a magnetic field, why don't the moving electrons create a magnetic field that gets pulled toward or away from the bar magnet instead of getting pushed up or down? 2: why does the moving electron behave as though is creates no magnetic field? 3: is the bar magnet really pushing the electron beam up or down because thats how a magnetic field interacts with an electric field?
The electron beam itself would create a magnetic field, and the electrons in the beam can even affect each other (both electric and magnetic forces). But these forces are all small compared to that of the bar magnet and they are not sufficient to affect the beam's momentum, so the particles move forward until the bar magnet pushes them.
@@InsideTheLoop Stern Gerlach was done with neutral atoms of the spins cause the magnetic force. Here we have a charged beam so the QVXB force is the main effect.
That one is so old that I think someone in the department made it. In fact, it often shocks you a bit when you flip the switches. If you watch I jerk my hand back quickly after flipping a switch. :)
Hola, profesor, disculpe que le escribo en español. Quería preguntarle si ha experimentado con dos tubos en paralelo, para observar la desviación de los haces de electrones, debido a sus propios campos magnéticos.
At college you pay to eat huge and clueless amount of knowledge, hoping one day your abstraction skills will put everything together to find a solution for a problem you were not exposed while being a student. This channel does the opposite, that is why I'm pushing the subscribe the button.
Could this be that the magnetic field changed the angular momentum of the charged particles? What would happened if you were to point the magnet from top or from bottom? If my theory is correct, the path of the charged particles would still follow the path.
Well the magnetic field does create an angular velocity for the electron thus creating angular momentum. And for pointing the magnet from top or bottom, the particles will move either right or left to it's original path according to the right hand rule.
At a basic level this is how fluorescent lights work. Rather than a beam of electrons, a large voltage is applied to "shake them free" of gas atoms, and then they accelerate and crash into gas atoms to emit light. Most of that light is UV, which excites phosphors on the walls of the fluorescent light (the reason they look white), which converts it to visible.
Alright please clear my doubts ... It is said that an electron in a magnetic field is not repelled nor pulled by either of the poles .. Why? And how a diamagnetic material magnetises? Or how is it able to produce magnetic field that repels the provided external field ? ...
An electron is only affected in motion. The formula is Q*v×B, the charge times the vector (cross) product of velocity and Flux density of the m-field. It is a great part of Einstein's ToR to understand how the motion of the electron plays in relativity.
@@Prof-Hafner Thank you sir. I was laughing at myself about my college days and how wonderful it is that I can stop your video and study it, and then follow your channel.
If it were a perfect vacuum there would be no light. There is a dilute gas in the tube so some of the electrons crash into gas atoms, excite them, and the atoms give off light.
@@Prof-Hafner Thanks for your reply! Isn't all light electromagnetic waves and photons? I was taught that light from the sun travels through the vacuum of space. Is the space between the sun and the earth not a perfect vacuum?
@@peterdaniel7663The path for light between the Sun and Earth is a very good vacuum, but obviously has some particles, like the solar wind, etc, probably a couple 100-1000 particles per cubic meter.
doesn't the cathode radiates its excess energy to be amplified by the only exit available thru the little slit to the ions in the tube, similar to a laser, and the cathode provides a path for the energy to flow back into. And what we see are not electrons but the radiation emitted as visual light from the ions in the vacuum tube. Is there other demonstration with zero ions insides the tube? Zero ions as measured at zero kelvin, no free ions energy in the vacuum which can demonstrate the flow of energy current only by the emission of "electrons".
@@ovidius2000 No, only the direction. That is approximating that I am applying a static field. Technically I move the magnet it and I pull it out, so I might be doing a small amount of work by creating a field that varies in time. But if you ignore that, then the static magnetic field can't change the speed of the electrons.
The source of an electron beam is usually a sharp metal wire that is heated and held at a strong negative potential. The thermal energy and electric field pull electrons out fo the metal. But electron beams are very limited in air at atmospheric pressure, so they are usually made in a vacuum tube.
thank you so much for this video. Visualizing the theory always helps!
thank you so much for this demo its so so useful 🙏🏻
whaaaat...
whoa. thank you for the demo. haven't seen someone do a practical of that before.
Wow this is dope!
thanks bro clutch video! very useful and concise :D
Thank you for making this video. :)
That is sooo amazing
Thanks for more understanding this concept.
Glad it was helpful!
wonderful!
WHAT HE SAID WAS
I can actually show you that with a real charged beam. So this is an evacuated tube and it puts a big negative potential on this electrode. So high that it actually boils, electrons come off the electrode and makes just a beam of electrons.
It also has some ionized, a little bit of a background gas that ionizes to keep everything stable and doesn't charge up too much. But mostly you have electrons flying off this electrode and most of them go straight to this metal plate and that's the end of the story.
But there's a little slit in the plate. So some of them get through and make a beam that keeps going. So you've got a beam of electrons and this little plate is tilted a little bit so they slowly along this direction they crash into the plate.
The plate has a phosphor on it so it lights up when they crash into the plate. So when I turn it on, there you can see the beam. That's a beam of electrons flying through the tube. So what we're going to do is bring a magnet and see what it does to the beam of electrons because remember this bar magnet, the field lines go from the north pole, the red is the north pole to the south pole.
So if we just think about the poles or the field right at the ends because we're going to use the ends, it will be this way near the north and it will be pointing in in the south. So I will bring the north pole pointing at me at the beam and let's see what that will be.
We have the beam going this way and I'm going to bring this pointing in so we're going to have a B field like this. So V cross B also the same as this. It should be up. So let's see what happens. There's our beam and I bring in this magnet.
There's the deflection we hope for but it's down and it's down and why is it down? It's down because they're electrons. Q in this case equals negative E. The charge is negative. When the charge is negative the force magnitude is negative which means it goes the opposite direction.
So right hand rule says it's up for positive but the force is down. for an electron. So it did deflect the right way. It deflected down. We can also check. We can take and aim the south pole at the beam.
So here we go. Bring in the south pole. And there it goes. It deflects up, just like you'd expect. Because when you're bringing the south pole, the magnetic field is pointing the opposite direction. Now I'm bringing in a field that's pointing away from the beam.
So it would seem that the charged particle beam really is deflected the direction that you would expect.
what a very nice demonstration of a charged particle trajectory
I am your new follower
This is how CRT display works
So that is a simplfied mass spectrometer
Awesome
If you can bend the beam with magnets I have one hell of an idea for flight thrust
The more interesting questions is, does a beam of electrons create a magnetic field? The relativistic explanations usually given for magnetic effect are very confusing.
@Physierge
1: if a moving electron creates a magnetic field, why don't the moving electrons create a magnetic field that gets pulled toward or away from the bar magnet instead of getting pushed up or down?
2: why does the moving electron behave as though is creates no magnetic field?
3: is the bar magnet really pushing the electron beam up or down because thats how a magnetic field interacts with an electric field?
The electron beam itself would create a magnetic field, and the electrons in the beam can even affect each other (both electric and magnetic forces). But these forces are all small compared to that of the bar magnet and they are not sufficient to affect the beam's momentum, so the particles move forward until the bar magnet pushes them.
@@Prof-Hafner How does it settle with the stern-gerlach experiment, does all of these electron have the same spin ?
@@InsideTheLoop Stern Gerlach was done with neutral atoms of the spins cause the magnetic force. Here we have a charged beam so the QVXB force is the main effect.
So that means cathode rays deflect perpendicular to magnetic field
I did this as a child with a magnet on my BW tv set.
Nice demonstration. From which company that electron beam demonstrator can we buy for our college? and what is its price?
That one is so old that I think someone in the department made it. In fact, it often shocks you a bit when you flip the switches. If you watch I jerk my hand back quickly after flipping a switch. :)
Hola, profesor, disculpe que le escribo en español. Quería preguntarle si ha experimentado con dos tubos en paralelo, para observar la desviación de los haces de electrones, debido a sus propios campos magnéticos.
At college you pay to eat huge and clueless amount of knowledge, hoping one day your abstraction skills will put everything together to find a solution for a problem you were not exposed while being a student. This channel does the opposite, that is why I'm pushing the subscribe the button.
Could this be that the magnetic field changed the angular momentum of the charged particles? What would happened if you were to point the magnet from top or from bottom? If my theory is correct, the path of the charged particles would still follow the path.
Well the magnetic field does create an angular velocity for the electron thus creating angular momentum. And for pointing the magnet from top or bottom, the particles will move either right or left to it's original path according to the right hand rule.
Maybe the russians in moscow will like some lessons on particle-electron beams.
I wish you were in my college
Sir, how much vacuum should be there? Will it work at 10^(-4) mbar vacuum?
Regards and Thanks
yeah, not sure about microscopes, but ebm printers are around that pressure
@@hyxl3r254Thanks sir.
It's a stupid question but can we use this as a light source?
At a basic level this is how fluorescent lights work. Rather than a beam of electrons, a large voltage is applied to "shake them free" of gas atoms, and then they accelerate and crash into gas atoms to emit light. Most of that light is UV, which excites phosphors on the walls of the fluorescent light (the reason they look white), which converts it to visible.
Alright please clear my doubts ...
It is said that an electron in a magnetic field is not repelled nor pulled by either of the poles ..
Why?
And how a diamagnetic material magnetises? Or how is it able to produce magnetic field that repels the provided external field ? ...
An electron is only affected in motion. The formula is Q*v×B, the charge times the vector (cross) product of velocity and Flux density of the m-field. It is a great part of Einstein's ToR to understand how the motion of the electron plays in relativity.
He said the an electron beam could carry a charge, what would happen if you sent a large charge in the beam and discharged it somehow?
What if you put the South Pole parallel to the beam at the opposite end of the tube? Would it turn into a standing wave?
It would coil. I think you see it nether in the other electron beam demo.
@@Prof-Hafner oh! duh. The right hand rule? I did see that demo…
Sir, how can we create a negative or any positive potential
You have to apply current to the electrodes
Nic it's ray gun's formula
They always erase the board before I am done writing it down.
--> Me...1980,81,82,83.
ruclips.net/video/N52M3TN9KDo/видео.html
@@Prof-Hafner Thank you sir.
I was laughing at myself about my college days and how wonderful it is that I can stop
your video and study it, and then follow your channel.
Do the electrons give off photons? If so, can you separate the photons from the electrons or ist it just a matter of imagination?
If it were a perfect vacuum there would be no light. There is a dilute gas in the tube so some of the electrons crash into gas atoms, excite them, and the atoms give off light.
@@Prof-Hafner Thanks for your reply! Isn't all light electromagnetic waves and photons? I was taught that light from the sun travels through the vacuum of space. Is the space between the sun and the earth not a perfect vacuum?
@@peterdaniel7663GoodObservation.inSpaceStarsAndSunAreNotVisible.SoSunDoesNotGenerateLight.RadiationFromTheSunIsConvertedToLightWheenItHitsTheAir.SunIsLikeACathodRadiatingInvisibleElectrons.AndTheEarthIsTheAnod.
This makes me need to take a seat and rethink life.
@@peterdaniel7663The path for light between the Sun and Earth is a very good vacuum, but obviously has some particles, like the solar wind, etc, probably a couple 100-1000 particles per cubic meter.
doesn't the cathode radiates its excess energy to be amplified by the only exit available thru the little slit to the ions in the tube, similar to a laser, and the cathode provides a path for the energy to flow back into. And what we see are not electrons but the radiation emitted as visual light from the ions in the vacuum tube. Is there other demonstration with zero ions insides the tube? Zero ions as measured at zero kelvin, no free ions energy in the vacuum which can demonstrate the flow of energy current only by the emission of "electrons".
I'm in 11th and I'm not getting it.
Why is it blue I thought cathode rays were greenish
It depends on what gases are in the tube. Also, in this case the color comes fro the paper.
Why is it blue
The light you see is actually excited gas atoms that were struck by electrons. The gases have characteristic colors. Like blue.
E|ectronsAreAlsoAcceleratedOrOnlyDeflected?
They are accelerated perpendicular to their motion, which causes the deflection.
@@Prof-Hafner IKnowTheVectorSpeedVaries,ButIWantedToKnowIfTheModuleValueOfTheSpeedIncreases.
@@ovidius2000 No, only the direction. That is approximating that I am applying a static field. Technically I move the magnet it and I pull it out, so I might be doing a small amount of work by creating a field that varies in time. But if you ignore that, then the static magnetic field can't change the speed of the electrons.
@@Prof-Hafner Ok.Thankyou.
How to make beam
The source of an electron beam is usually a sharp metal wire that is heated and held at a strong negative potential. The thermal energy and electric field pull electrons out fo the metal. But electron beams are very limited in air at atmospheric pressure, so they are usually made in a vacuum tube.
Sir,how can we create a strong negative potential
this shit is not even fake
You rmember me thé Kaaba..mekka..wich thé Muslims turn around like magnétique positions.