Charged particle in a magnetic field

[SharinganFY]

in which direction is the initial velocity of the particle??

[mechanicalbu11]

i do not understand why the point charge is revolving, should it be moving to the left linearly or perpendicularly to the field? what force is making the point charge behave in a radius motion?

[evhgl87]

magnetic field vectors point in the opposite direction of expected current flow with the magnitude of the vectors shown here as elongated lines (the arrows should be at the end to show a vector though, not centered). it is a proton particle, therefore the motion in the video is indeed correct. thanks for sharing.

[PelletierPhysics]

@evhgl87 The arrows are centered because these are magnetic field lines, not magnetic field vectors. The magnitude of the magnetic field is proportional to the density of the lines instead of being proportional to their length.

[evhgl87]

@PelletierPhysics interesting they do not teach this in upper level introductory physics? learn something new every day. is the density an indication of relative thickness or simply a viewing of transparency?

[PelletierPhysics]

@evhgl87 Magnetic field lines are used in all my electromagnetism textbooks. The magnetic field is stronger where the lines are closer to each other, and weaker where there is a larger distance between the lines. What textbook did you use?

[evhgl87]

@PelletierPhysics I looked into my textbook from previous semesters and they are indeed briefly indexed, but never instructed. The professor was a PHD graduate from Brazil but knew very little about electronics, possible that this mixed with a language barrier could be to blame. Thanks again for sharing.

[nero314100]

you have the direction backwards, that would be the direction for a negatively charged particle and it looked like your particle had a plus on it.

[PelletierPhysics]

@nero314100 It is a positive charge and the motion in the video is correct.

[nero314100]

@PelletierPhysics according to the right hand rule you should be able to point your thumb on your right hand in the direction of the B field and your fingers will curl in the direction the current will follow, aka the particle in this case. right thumb up, fingers curled counter-clockwise. your particle travels clockwise, so it is wrong.

[PelletierPhysics]

@nero314100 What you describe would be correct for a magnetic field caused by the motion of the charged particle.  Here the particle is not the cause of the magnetic field. The magnetic field produces a magnetic force directed toward the center (centripetal force).

[YamiPoyo]

@PelletierPhysics centripetal force has nothing to do with electro dynamics.

[PelletierPhysics]

@YamiPoyo You hypothesis is interesting, but there's a centripetal force in every circular motion, even when the particle in circular motion has an electric charge...

[FlubsyMalone]

@PelletierPhysics it would go in the other direction if it was a negatively charged particle... so the video's correct

[MrChloroflorocarbon]

You have posted 34 videos which are really great. Please keep on going

[SeriousNot]

Now I understand how the Joe Cell works. I am referring to the cell invented in about 1991 by Joseph Cate in Australia. The charged particle is accellerated with sufficient force to quantum tunnel through the engine block into the combustion chamber where electron capture and oxygen and hydrogen recombination occur providing enough force to pull the piston upwards and beyond TDC. This is why it is important to use seamless tube to avoid paramagnetism that occurs during welding.

[RobDeManc]

Can anyone describe what a "field" is? How should I visualise it? I currently visualise it as a cloud.

[chehar]

flemmings right hand rule

[drewser1303]

You should clarify what you're doing in this video. The particle starts with some initial velocity in the direction of external magnetic field. Since, in this case, v x B = 0 it just continues with constant velocity. You also start the particle with some initial velocity perpendicular to the magnetic field. In this case, you generate the lorentz force F = q (v x B). Since v_initial is out towards us, B is up, v x B gives a force to the left and you get your cyclotron motion.

[jeras97]

how I can get this program??

how to download it??

[PelletierPhysics]

@jeras97

Povray web site.

[dark3lf1337]

@PelletierPhysics Thanks bro, maybe a link next time?

[carbon0f1ce]

right hand thumb rule? shouldnt the arrows be pointing downwards?

[PelletierPhysics]

@carbon0f1ce The green arrows are not the magnetic field produced by the charge in motion, they represent an external magnetic field in which the charge moves.

[gikiian]

@PelletierPhysics i still don't get it :$

[SHENAKU]

this stuff is too confusing to me XD 0o0

[gjohn1000]

i have a question, why does it make a difference in the direction of the force, when there is a negatively charged particle, as oppose to a positively charged particle?

[julianmp]

to #davidexxx

PROTONS in a magnetic field...

[madscirat]

Very cool, thanks

[davidexxx]

ELECTRONS IN MAGNETIC FIELD!

[dinkarilu]

so the particle moves about the magnetic field and not along it that is not parallel to magnetic field. it was confusing me since long. the video was very helpful. thanks to uploader.

[jajnic]

The initial velocity of this charge was not perpendicular to the magnetic field lines, and that is why it moves on helix instead of just a circle?

[PelletierPhysics]

Yes, you are right.

[definitionofis]

I thought it was a helix because the revolution of the particle creates a magnetic field (like a simple electromagnet) which interacts with the external magnetic field.

[interstitialofficial]

Is this how magnetrons work?

[RyuDarragh]

The reason for the right hand rule is the spin of the particle in relation to its momentum is clockwise. The best explanation for this is that the initial conditions were 50-50 (like any good coin toss) and the universe landed heads up. Had initial conditions been different, we'd never notice the difference.

[vocalpatriot]

Point taken. But universal coin toss? sheesh..

[tzone92]

Lol, I like the idea of a "universe coin" being tossed.

[Beamshipcaptain]

This is the basis of Radio, and wireless power-transmission. All charged particles in a radio-wave or microwave-beam must follow a helical-path. On a two-dimesional CRT, they look like a sine-wave.

[PelletierPhysics]

There is an upward component. But there is also an horizontal component (tangent to the circle). Without the upward component (parallel to the magnetic field), the motion would be circular.

[franksui]

the horizontal component is just like circular motion isn't it?

[12345rehan]

send sum more like this

[postmoderntool]

Why does it spin Clockwise?

[PelletierPhysics]

The magnetic force is directed toward the center of the circle.

[seljer]

F = e * (v x B)

with v and B being vectors, and the cross product giving a vector perpendicular to both v and B

and since its always perpendicular to the velocity, its working as a centripental force = circular path

clockwise...because of that entire right-hand rule thing (v is before B)

if the charge were opposite then it'd be spilling in the other direction

[ertreri]

"with v and B being vectors, and the cross product giving a vector perpendicular to both v and B"

Still don't get it!

V is constant right? and B likewise?

So the cross product would/should yield always the same upwards prependicular vector.

And F does not change according to the position of the charge, than you should get a linear trajectory... no?

[PelletierPhysics]

@ertreri

The cross product is not upward (it can't be parallel to the magnetic field).

The cross product is horizontal, directed toward the center (perpendicular to velocity and magnetic field).

[Yakeyglee]

@ertreri v is not constant. The magnitude is, but the vector value is not. The vector value is always changing, which is why the cross product between it and B is always changing (i.e. - always pointing towards the center of the circle).

[tcepsa]

@ertreri Also, the magnitude of v is constant but its direction is changed by the force acting on the charged particle in the manner that @PelletierPhysics described

[gurser]

postmoderntool: i believe it turns clockwise because its a positive charge. If it were a negative charge eg. an electron as in seljer's equation, then it would turn the other way.

[inside5stars]

very nice and useful animation