Calculate Induced EMF in Circular Loop: Cylindrical Coordinates

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Discussion Overview

The discussion revolves around calculating the induced electromotive force (EMF) in a circular loop moving within a uniform magnetic field, specifically using cylindrical coordinates. Participants explore the relationships between the magnetic field, electric field, and induced EMF, while addressing potential conceptual and calculation errors.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant discusses the curl of the induced electric field in a cylindrical coordinate system, suggesting that the electric field components in the radial and axial directions are zero, leading to a focus on the azimuthal component.
  • Another participant introduces the concept of magnetic flux as the product of the magnetic field and the projection of the loop area perpendicular to the magnetic field.
  • A subsequent post provides a formula for EMF as the negative time derivative of magnetic flux, specifying the flux in terms of the loop's area and its angular position over time.
  • A correction is made regarding the loop's rotation, clarifying the projection area and reaffirming the expression for magnetic flux with respect to the loop's rotational speed.

Areas of Agreement / Disagreement

Participants present various approaches and formulas related to the calculation of induced EMF and magnetic flux, but no consensus is reached on the correctness of the methods or the expressions used. Multiple competing views and interpretations remain evident throughout the discussion.

Contextual Notes

There are unresolved assumptions regarding the definitions of variables and the specific conditions under which the calculations are made. The discussion includes potential conceptual errors and varying interpretations of the relationships between the magnetic field, electric field, and induced EMF.

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TL;DR
How can I express the induced EMF in terms of the radius of the loop, through a uniform yet changing B field, in order to calculate the curl of the induced electric field?
In order to calculate for the curl of the induced electric field for a loop moving in a uniform magnetic field, and using the cylindrical coordinate system for a curl, it's my understanding that since the B field is in the 𝑧̂ direction, then so is the partial time derivative of B, and therefore its curl. So in terms of cylindrical coordinate system, the 𝑠̂ , 𝜙̂ cancel out and with respect to electric field the 𝐸𝑠 and 𝐸𝑧 is simply zero. So we are left with the curl of the electric field in the 𝑧̂ direction and the electric field in the 𝐸𝜙. And we ultimately end up with:
∇×𝐸⃗ =𝑧̂ [1/𝑟 ∂/∂𝑟 (𝑉𝑖𝑛𝑑𝑢𝑐𝑒𝑑/2𝜋𝑟)]
So here, how do I write the 𝑉𝑖𝑛𝑑𝑢𝑐𝑒𝑑 in terms of s, to calculate for the partial "s" derivative, and therefore calculate the magnitude of the curl. If there's any conceptual or calculation errors, please do suggest where I have gone wrong.
 
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The magnetic flux has to be the product of B and the projection of the loop area on a surface perpendicular to B. α=2*pi()*s*t
loop rotating in magnetic field.jpg
 
Sorry. I forgot to mention:
Emf=-dφ/dt ; φ=B*pi()*r^2*cos(2*pi()*s*t)^2 ;s=speed [rps]
I=Emf/Zloop
E[electric field]=ρ*J [current density];ρ=loop resistivity.
J=I/loop cross section area.
 
:oops:Correction:

Let's say the loop rotates about a diameter with s rotations per second[rps].

Then the loop projection area will be п*r^2*cos(α)

α=2*п *s*t and the magnetic flux will be:

φ=B*п*r^2*cos(2*п*s*t)

*=multiply by [x] as in Microsoft excel
 

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