Emf induced in rod traveling through magnetic field | Physics | Khan Academy

Emf induced in rod traveling through magnetic field.

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[zakirhussain-jsku]

The length of rod is constant, so are magnetic flux and velocity. How can flux change if nothing is changing. Only change is motion of rod relative to the flux. Instead of changing flux we should say moving magnetic flux induces emf in a conductor due to relative motion b/w rod & flux. To calculate total moving flux, area in the direction of motion & flux density in this area is relevant.

[gitersaras]

Thanks, I hoped I had you as a teacher....

[ajayananthakrishnan]

I guess another way to think about this is to use the Lorentz force. As the bar moves to the right, it has a constant velocity. Therefore, using the right hand rule, the force, q x v x B, will point from the top of the rod to the bottom. This force will cause separation of positive and negative charges in the rod (positive charge will go to the bottom, negative to the top). Therefore, an electric field will be generated in the bar, and this in turn causes an EMF in the loop, causing current to flow.

But my question is, can we think of this EMF in terms of a voltage drop? As in, can we just think of it as a battery in the place of the rod, with the positive terminal at the bottom and negative terminal at the top? This is what makes the most sense to me, but this way of visualizing EMF seems to break down in other examples such as moving a bar magnet through a solenoid, etc. So what exactly is an EMF?

[tahahussain]

Can someone explain how there is a change in the area? since the size of the rod doesn't change

[poonamdevi]

Please provide this video in hinglish just because more understanding

[SatyamKumar-tsjh]

My question is "But Why"??
Why is an emf induced when there is a change in flux??
Please clear my doubt.

[siddhantacharya]

If the rod was going left instead, then the current induced would be counter clockwise, right? Because the magnetic field of the area that the rod is sweeping in that case increases with area which needs to be reduced. Isn’t it ?

[abro]

This example is great! Can you do one with the rod being pulled by force MG through a frictionless pulley? Or how to get velocity as a function of time.?

[gabriellamonterrosa]

wouldn't the current be counterclockwise to combat the increase in flux?

[momensaid]

thanks you had simplified this theory
i wish i had a professor like you

[oreosxking]

Why is there a change in area? Does the 'area' refer to the area of the loop between the cylinder and wire or just the surface area of the cylinder perpendicular to the magnetic field? Pease help I'm so confused.

[alanx]

the enclosed area in the formula has nothing to do with reality, it's a mathematical artifact, bvl shows this, a closed area is just the result of a closed circuit.

[RubenAlvarezMtz]

I was looking through the website and couldn't find the section that has these videos.

[xxxx-fwkk]

Towards the end of the video he gives the direction. But since its a straight rod, wouldn't it generate a circular magnetic field??? I.e if you keep curling your fingers you will find that it continues to come out of the page again..because currents produce field lines that form loops...so...

[rationalthinker]

What about the vector directions? Would it not be more comprehensive to show that emf = Closed line integral of velocity vector cross product magnetic field vector dotted with the differential length vector

[MATHBOSS]

how is the area changing. same rod same magnetic flux.

[stevendusseau]

Good explanation up until the last part of the video. I do understand that straight wires have a circular current. I'm just confused why other videos, from other people, have drawn straight current lines? Is it because, as the induced magnetic field goes downward, around the wire, and as it hits the perpendicular point, it directly opposes the magnetic field?

[calculasians]

right hand drawing skillz on point. Also, at the end, did you mean that the current should be going counterclockwise? BC if you align your hand to what you drew at 7:17 the fingers curl around counterclockwise if I'm not mistaken,

[franciscomaerle]

I wish this formula could be described to its vector form v x B, and not using Δ

[AldenPez]

This was explained really well. Thank you. But the "our change in.." counter reads 19 lol