Right Hand Rule TBR Physics Passage V, Question 32

[deleted388502]

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Conceptual question on the RHR.

So question 32 in Passage V talks about moving a loop through a downward magnetic field, going from right to left, and asks what type of current it feels upon exiting the field while moving to the left. I got the right answer by doing a right hand rule considering only the direction of the B field. is it important to consider direction of velocity in this case?

That leads me to my next question; how do you know whether the current induced in the loop is opposite to the magnetic field? For example, when this loop enters the downward magnetic field, it will experience this "new" magnetic field and produce current that creates a magnetic field opposing the new one it's entering. That's the concept behind flux (unless I'm mistaken).

Now, I'm confused as to what happens as it continues going through the field. As the loop becomes more immersed in this downward facing magnetic field, doesn't it just continue to create the opposing magnetic field with induced current (so, a current that would create an upward magnetic field)? Upon leaving the downward magnetic field, why is it producing induced current in the direction of the magnetic field that it was in? TBR's explanation to this question implies that it's producing induced current upon exiting that is in the direction of the magnetic field it's leaving.

Also related to this, why does moving the loop into the field faster make more induced current?

Lots of questions here about B fields, they've always confused me! Any help is appreciated.

 

[lNVlNClBLE]

Any current produced in a loop entering/exiting a magnetic field will always be opposite to the change in flux. For instance, if a loop enters a magnetic field and increases its flux, the induced current will "oppose" this change. In this case the flux is changing because the area of the flux within the loop changes as it first enters a B field.

As the loop first enters the field, the flux increases, and it induces a current until it is fully within the field. After the loop is entirely immersed in the field, there is no current because the magnetic flux is not changing. As the loop exits the magnetic field on the other side, you see the opposite induced current because the flux is now decreasing as it exits the field. And once it is completely outside of the magnetic field on the opposite side, the current is again zero.

A loop moving into a field faster makes more induced current because its area, and thus flux, is changing at a faster rate.

I like to think of Lenz's Law like Le Chatelier's Principle.

 

[deleted388502]

Any current produced in a loop entering/exiting a magnetic field will always be opposite to the change in flux. For instance, if a loop enters a magnetic field and increases its flux, the induced current will "oppose" this change. In this case the flux is changing because the area of the flux within the loop changes as it first enters a B field.

As the loop first enters the field, the flux increases, and it induces a current until it is fully within the field. After the loop is entirely immersed in the field, there is no current because the magnetic flux is not changing. As the loop exits the magnetic field on the other side, you see the opposite induced current because the flux is now decreasing as it exits the field. And once it is completely outside of the magnetic field on the opposite side, the current is again zero.

A loop moving into a field faster makes more induced current because its area, and thus flux, is changing at a faster rate.

I like to think of Lenz's Law like Le Chatelier's Principle.

Beautiful explanation, made perfect sense and I don't think I'll ever get confused about this again. THANK YOU!