Motional EMF

Physics Ninja loos at calculating the motional EMF, current (direction and magnitude), Force, Power when a conducting rod is dragged in a region with a magnetic field. At the end of the video i also look at a different approach to the same problem using Faraday's Law.

[krishnannarayanan]

The final part where you said to compensate for the change in magnetic flux due to increase in area, a current is induced such that to counteract that magnetic flux made so much sense. Thank you!

[hesarafonseka]

Thank you so much, he explains better than my professors

[sydneyfarina]

Thank you so much!! This helped me a lot for my final tomorrow :)

[markkennedy]

Hi, thanks for this.
Just about the F=ILB acting on the rod where I is the current in the rod (due to the vertical velocity of the charge carriers in the rod). Can you explain why we do not consider the rod's horizontal velocity also when getting the magnetic force B on the charge carriers in the rod. Why ignore this horizontal component v of the rod (and its charge carriers)?

More broadly, is there a F=ILB on the other sections of the loop due to the velocity along the wire of their charge carriers. I know it won't cause displacement of these sections but does such a force exist due to their velocities? This is something I don't understand about the extent of self-induction that you may be able to clarify.

[minhokim]

Hi Ninja, I got a question on your explanation on 3:15 of the video. Electrons are supplied by the loop, so there isn't a buildup of positive charges! The charge balance would be neutral or zero over the entire loop. Could you please reply to me? Thanks very much, Ninja. I like to watch your vids very much and I am your fan.

[MuqtadaMO]

I watched the video from Iraq and thank you my friend

[ياسينبونو-كض]

I am an arabian but i study physic in english language
I' ve understand you and thanks for great job

[claytonhouser]

For anyone else confused on why the first magnetic force points downwards when using right hand rule...REMEBER we are talking about a negative particle. NOT a positive particle. THe magnetic force for a negative particle points int he OPPISIOTE direction a positive ones force points.

[HK-cqyf]

What about the forces on the rod due to the parallel part of the circuit? They both have current which create fields on each other, which then would create attractive forces, right? Or is it negligible?

[nicolasabramlujan]

Thanks a lot for the video, understood it a lot better than I did in my class 😅 Though I did have one question about the first part using motional EMF
Since there is a current being generated in the left side of the circuit, moving downwards, would that also generate an Fb? (Which would be opposite to the one on the right side of the circuit, so going right instead of left)
If there is, wouldn that not already cancel out the force generated on the right side bar?

[YadelewAsrie]

I love you too because of your best explanation keep it up!!!

[ndiogouniang]

You really called the lecture. At some point I tought you'd say "Touchdown Faraday!!"

[كيموهيرو]

does the direction of force Fb =ILB should be to the left because the charge is negative ?

[michaellamoreaux]

The emf is motional emf. The change of flux linking the circuit has no effect. There are two independent principles called induction. They are motional emf and transformer emf. Transformer emf is expressed by the Maxwell-Faraday Law, which is one of Maxwell's equations. An intrinsically changing flux is accompanied by an electric field. A change of flux due to a change in exposure of a circuit to a magnetic field is not. Therefore, Faraday's Law is not a law, just math.

[utkarshprithviraj]

If magnetic force is in the direction of displacement of the electrons ....work is done by magnetic field but this isn't possible right....?

[roseyousif]

bro, like from where did we actually get the original v isn't it from external work? and also yes the current will move to the opposite direction of velocity but this happens in a fraction of a second the force will come back from the other end of the wire and it will be in the same direction of velocity so, in the same way, it decreases it will increase in the fraction of a second.
the thing is we should apply force from the beginning to get the charges to move in the first place but there is friction so we should keep adding force and also there is resistance in the wire which will get the charges to slow down so that is why we should add the external force, I really need to understand this but it is just not logical to me

[guillaume]

Damm, incredible explanation. Thanks!

[fatemusik]

I'm trying to solve a certain acceleration the rod gets from rest when the circuit has a dc source in it while in a uniform magnetic field. I still have no clue how to approach the final value formula. All I know is that it has something to do with Lorentz's force, Newton's II law and Faraday's law. unfortunately this video didn't help me get on the right tracks either. (I think it's a bit more advanced computation?)

[raneemalbadi]

Is induced current by frhr the direction of e flow or conventional current?

[zacharialameck]

Yes concepts are so great making me more knowledgeable bt the only challenge I face is all about Fb and Fapp directions why are in those sence.