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baseballfan_ny

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I'm in an intro E&M class, and I'm trying to distinguish between Motional EMF for loops of wire and conducting plates. This question might be kind of silly, but are Eddy currents pretty much the same thing as induced currents in a loop of wire? More specifically, what I am trying to ask is if the resistive slow down in the Motional EMF cases for a loop of wire and a conducting plate can both be explained by Lorentz forces and Joule Heating/Power loss.

(Image Credits: 8.02.3x, MITx)

In this above example of motional EMF, considering the case when the loop of wire enters the magnetic field, a counterclockwise current is induced by Lenz's Law. The right most leg of the loop will experience a Lorentz force in the -##\hat i## direction, and this resistive force will slow the loop down. That's the explanation I've seen in class. But what I'm wondering is if this slow down could also be attributed to the Joule Heating and Power loss that occurs as an induced current flows through the wire? This would decrease the Kinetic Energy and slow it down -- is that a valid way to see it in this case? Because in my E&M classes I've never seen that explanation used for loops of wire in the Motional EMF case and it seems to always be reserved for describing Eddy currents.

(Image Credits: 8.02.3x, MITx)

In the same way, when talking about Eddy currents induced on a conducting plate, could we also describe the reason for the slowdown in terms of resistive Lorentz forces? In this above case, clockwise Eddy currents will be induced such that the downwards Eddy currents on the right are "more immersed" in the magnetic field, so they will dominate in terms of Lorentz forces. These downwards currents cause a Lorentz force in the -##\hat i## direction, a resistive force that slows the plate down? I've never seen this explanation for Eddy currents slowing a plate down -- it is always explained in terms of Joule Heating and Kinetic Energy loss. So I'm wondering if this Lorentz force explanation is even valid?

Essentially, I'm asking if the Motional EMF example for a loop of wire can be explained in terms of Joule Heating and Power loss and if the Motional EMF example for a conducting plate can be explained in terms of Lorentz forces.

Edit: Last sentence is kind of misleading. What I mean is: Essentially, I'm asking if

(Image Credits: 8.02.3x, MITx)

In this above example of motional EMF, considering the case when the loop of wire enters the magnetic field, a counterclockwise current is induced by Lenz's Law. The right most leg of the loop will experience a Lorentz force in the -##\hat i## direction, and this resistive force will slow the loop down. That's the explanation I've seen in class. But what I'm wondering is if this slow down could also be attributed to the Joule Heating and Power loss that occurs as an induced current flows through the wire? This would decrease the Kinetic Energy and slow it down -- is that a valid way to see it in this case? Because in my E&M classes I've never seen that explanation used for loops of wire in the Motional EMF case and it seems to always be reserved for describing Eddy currents.

(Image Credits: 8.02.3x, MITx)

In the same way, when talking about Eddy currents induced on a conducting plate, could we also describe the reason for the slowdown in terms of resistive Lorentz forces? In this above case, clockwise Eddy currents will be induced such that the downwards Eddy currents on the right are "more immersed" in the magnetic field, so they will dominate in terms of Lorentz forces. These downwards currents cause a Lorentz force in the -##\hat i## direction, a resistive force that slows the plate down? I've never seen this explanation for Eddy currents slowing a plate down -- it is always explained in terms of Joule Heating and Kinetic Energy loss. So I'm wondering if this Lorentz force explanation is even valid?

Essentially, I'm asking if the Motional EMF example for a loop of wire can be explained in terms of Joule Heating and Power loss and if the Motional EMF example for a conducting plate can be explained in terms of Lorentz forces.

Edit: Last sentence is kind of misleading. What I mean is: Essentially, I'm asking if

*the resistive slow down*in the Motional EMF example for a loop of wire can*also*be explained in terms of Joule Heating and Power loss and if the Motional EMF example for a conducting plate can*also*be explained in terms of Lorentz forces.#### Attachments

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