Physics 43 Magnetic Forces on Moving Charges (2 of 26) Direction and Magnitude

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In this video I will calculate the magnitude and direction of the acceleration of a charged particle in a magnetic field.

[@sharrysingh4243]

Thank You so much Mr. Biezen! Because of you, I got 93 on my physics exam! Love your video and you do such a great job explaining the problems and the concepts.

[@MichelvanBiezen]

+Rice Spice Great job! Keep up the good work.

[@austinhaider105]

Love the breakdown of the units from Tesla’s to the answer.. it seems like so many professors overlook the benefit that an intuition of units can give. Your one of the best physics lecturers I’ve seen and certainly the best one on KZbin. Thank you for your edification!

[@MichelvanBiezen]

The Weirdologist, But we are not doing X x Y. The direction of the force is determined by v x B Therefore it is in the negative z direction

[@Jc123]

For anyone confused on the direction of the Magnetic force. You can always check your work by taking the cross product of the direction (Unit) vectors Being that i hat = j hat = and k hat = < 0,0,1> j X i = -k Or in other words the direction of the Magnetic force. is in the negative z axis

[@oqhr]

thank you for the effort. your lessons are really helpful and clear

[@ThousandGigs]

without you I wouldn't sand a chance against my physics exams. Thanks from south africa

[@MichelvanBiezen]

Great that these videos are helping. Keep up the hard work.

[@Paperman299]

This has been commented so many times but you are legit amazing

[@iammoonjooyoung]

Better than my professor.

[@emiliaborjavelarde721]

thank you so much!!! your videos are truly amazing, you help me a lot

[@vidaflowmotion]

Why is the angle 90 degrees? The magnetic field is slanting downwards, thus shouldn't the angle between V and B be less than 90 degrees?

[@valeriereid2337]

Thanks so much for explaining the units at the end and not missing any step. I needed this!

[@MichelvanBiezen]

Glad it was helpful!

[@MichelvanBiezen]

Glad you found our videos. 🙂

[@LoVeToPMTeTo]

he's the best

[@chillinandconflictin]

Why was the y component not included in the Magnetic Field calculation? If you're crossing it, shouldn't it be x?

[@MichelvanBiezen]

You only need the perpendicular component.

[@izhakbar]

thank you so much. REALLY.

[@kaylachoi4791]

can you explain how to use the right hand rule in getting the direction for the acceleration? So the x direction would be where your fingers point and the positive y direction where your fingers curl, and the thumb would be the acceleration?

[@ridwan7410]

Thanks for the class. It was very helpful. One little confusion I had been having. From where are you using the formula F=q(v*B)..I mean is there any proof of the derivation of that formula? Is it included in this segment? I would be very much obliged to get some heads up about the problems I had been having. Thanks once again.

[@bonnieandersona.brandao2677]

I love you!!!! for sure = DD

[@carolinek1039]

Hello Mr. Biezen, I hope you're doing well. When I solved the problem, I found the magnitude of the vector B and said that the angle between V and B is (90+26.56) and I got the same result as yours, is this method accurate?

[@MichelvanBiezen]

Yes, you will get the correct magnitude that way.

[@alvarozerkowski3706]

I didnt know the units for T. Cool.

[@chibingwei761]

sir，what rule you use?can use Fleming left hand rule or not?

[@MichelvanBiezen]

You can use the Fleming left hand rule. You will get the same result.

[@chibingwei761]

Michel van Biezen sir use what method?

[@MichelvanBiezen]

If you go to the beginning of the playlist (the first videos) you can see how the technique works.

[@joel.103]

Hi prof. I was wondering, isn't the magnitude of the Force supposed to be calculated with the angle between v and the B? You considered the angle between v and the X axis...

[@MichelvanBiezen]

+JLion ofZion We multiplied v with the x-component of the B-field. (which is the perpendicular component to v)

[@norhidayah7654]

It is stated that v parallel to y axis so there's no force and thats why we only consider x axis

[@hasibullahmahmood7457]

darkbrown _ You make it more clear, thank you

[@bit9103]

Why did you draw the magnetic field lines as if they are going down , in the question they did not mention anything about the way we should draw the magnetic field so what made you decide to draw it in that way ? and what is that sign that you draw on top of vector F and the others ?

[@MichelvanBiezen]

The direction of the magnetic field was given in the problem as a vector field. The symbol on top of the letter representing vectors is an arrow.

[@bit9103]

@@MichelvanBiezen A vector field always points down the same way you drew it and at that angle as well ? and thank you for replying !

[@iLavaRF]

Is the acceleration that you calculated, the radial acceleration?

[@MichelvanBiezen]

That is the tangential acceleration (along the curve of the path).

[@mrclutch5500]

So is z basically the opposite of whether the charge is into or out of the board?

[@MichelvanBiezen]

+Mr Clutch Yes, positive z is out of the board and negative z is into the board.

[@mrclutch5500]

ok thanks for the help

[@shahwali4291]

sir how you assume the magnetic field in a direction as shown above?

[@MichelvanBiezen]

The direction of the magnetic field is a "given" in the problem for the purpose of illustration. (we didn't have to figure it out).

[@shahwali4291]

Michel van Biezen sir i am asking about the way you draw the B field lines.

[@MichelvanBiezen]

Once you know the direction of the field you simply draw arrows. If the field goes into the board we draw "crosses". If the field comes out of the board, we draw dots.

[@TheWeirdologist]

Shouldn't the force be in the positive z-axis (+k)? X x Y is Z, isn't it?

[@lorieannalmandres4663]

yes, same question...

[@TheWeirdologist]

@@lorieannalmandres4663 this was Michel's comment on my post: "But we are not doing X x Y. The direction of the force is determined by v x B Therefore it is in the negative z direction"

[@4draven418]

Hello, Michel van Biezen. Why is there no sound just on these 1-6 videos? video 7 onward...no problem. I had watched them a while back and recommended them to a friend who wanted refreshers on the subject. He said that there was no sound.

[@MichelvanBiezen]

Our older videos were recorded in mono sound (before we figured out what we were doing). Sound will come out on one side.

[@4draven418]

@@MichelvanBiezen Thank you for your reply. Re setting sound out put doesn't work. But never mind, my friend said he will use the subtitle after all, is is only 1 to 6 that are affect. Thank you again.

[@asaadalalawi3561]

this a centripetal acceleration right?, so the actual speed does't change but direction?

[@MichelvanBiezen]

The force and acceleration found here is the instantaneous force and acceleration (magnitude and direction). Since the motion of the charge is not perpendicular to the magnetic field, the eventual motion will not be circular (initially) and therefore the motion is not strictly centripetal. Once the motion of the charge is perpendicular to the magnetic field the charge will move in a circular path.

[@asaadalalawi3561]

@@MichelvanBiezen Thank you professor.

[@hythe4936]

How do you know the direction is into the board

[@MichelvanBiezen]

Using the right hand rule. We have a video on that (I believe it is the first one in the playlist)

[@user-rb3ww3yl5d]

I have a question. 1.5*10^-3 kg^2*9.8m/s^2 is a very big number compared with 2*10^-3 N,then why is the force of gravity negligible in this case?

[@MichelvanBiezen]

In this problem we chose to ignore gravity. If we take the x-y plane to be horizontal, gravity would not be a factor in the x-y direction.

[@user-rb3ww3yl5d]

Michel van Biezen Thank you very much for answering my question!

[@hamzahazzam668]

Why -10Tj, is not be written in formula?

[@emiliobascary4793]

the force should be in the positive z-axis direction

[@MichelvanBiezen]

The force on the moving charge is drawn correctly as drawn "into the board". Thanks for checking.

[@emiliobascary4793]

I´m confused, the force shouldn´t not be popping out the board?

[@MichelvanBiezen]

The way to check is to take your right hand (since it is a positive charge), point your finger in the direction of motion of the charge (up) and then curl your fingers in the direction of the magnetic field (to the right). Your thumb will point in the direction of the force.

[@markjaypar5622]

My brain be like:🤔whatttttttttt!!!!!!!!

[@lorieannalmandres4663]

isn't X x Y or the +z direction into the page? thank youu

[@MichelvanBiezen]

As indicated in the video, the direction of the force is in the negative z-direction. (v x B) Not that the positive charge is moving in the positive y direction

[@lorieannalmandres4663]

@@MichelvanBiezen Thank you for your response :) but I'm quite confused in the 5:14 timestamp when you said that the +z direction is out of the page. May I ask what variables did you cross each other with?

[@MichelvanBiezen]

X x Y is indeed a vector that points in the positive z direction. But in this problem the motion of the positive charge in in the y -direction and the horizontal component of the B-field is in the positive x - direction. Therefore Y x X is a vector in the negative z-direction.

[@lorieannalmandres4663]

@@MichelvanBiezen ohh! that is why! you're the best prof out there, mr. biezen! I have been relying on your physics lectures this semester because i think your videos are the most comprehensive and easy to understand. I owe my grades to you 😁 Cheers to helping more people like me 🥺 I wish you the best and please stay safe!! 💟

[@MichelvanBiezen]

Thank you and glad we are able to help.

[@wawanhitam]

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