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yungman
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As the tittle, can varying magnetic field ( well EM) cause eddy current in non magnetic conductors like aluminum? If so, why?
Thanks
Alan
Thanks
Alan
yungman said:As the tittle, can varying magnetic field ( well EM) cause eddy current in non magnetic conductors like aluminum? If so, why?
Thanks
Alan
Bob S said:Eddy currents arise from [itex]\nabla \mathrm{x} \overrightarrow{E}= -\mu\mu_o \frac{\partial \overrightarrow{H} }{\partial t}[/itex]
A varying magnetic field can induce currents in any electrical conductor, both magnetic and non-magnetic.
For flat surfaces, it is straight exponentialCreator said:Is there an equation that gives me the depth of the current induced ?
Bob S said:For flat surfaces, it is straight exponential
[tex] i\left(z \right)=i\left(0 \right)e^{-\left(\frac{\mu\omega}{2\rho} \right)^{1/2}z} [/tex]
For curved surfaces, it is given by the ratio of two modified Bessel functions of order 0 with complex arguments. See chapter 10 in Smythe
Static and Dynamic Electricity (3rd Edition)
Thanks Bob, but I can't read the tiny print ...looks like inverse exp. sqrt power of: {(magnetic permiability of material x frequency) / 2 x current density} x z ??Bob S said:For flat surfaces, it is straight exponential
i\left(z \right)=i\left(0 \right)e^{-\left(\frac{\mu\omega}{2\rho} \right)^{1/2}z}
The skin depth is [itex] \delta=\left(\frac{2\rho}{\omega\mu} \right)^{\frac{1}{2}} [/itex] where ρ is resistivity.yungman said:Is ρ supposed to be σ ?
[tex] Ln\left(\frac{i\left(z \right)}{i\left(0 \right)} \right)=-\left(\frac{\mu\omega}{2\rho} \right)^{\frac{1}{2}}z [/tex]Creator said:Thanks Bob, but I can't read it ...looks like inverse exp. sqrt power of: {(magnetic perm
Thus ...
ln[I(z)/I(0)] = ln[e^-(...)] = -sqrt(uw/2p)(z)...ln = nat log; I = current.
Thus...
z = ln[I(z)/I(0)] / -sqrt(uw/2p)...where u = mu; w = omega, and p = rho.
Correct?
Bob S said:The skin depth is [itex] \delta=\left(\frac{2\rho}{\omega\mu} \right)^{\frac{1}{2}} [/itex] where ρ is resistivity.
See http://www.rfcafe.com/references/electrical/skin-depth.htmyungman said:So Eddy current is a totally different mechanism from free surface current according to the magnetic boundary condition?
Bob S said:
Bob S said:[tex] Ln\left(\frac{i\left(z \right)}{i\left(0 \right)} \right)=-\left(\frac{\mu\omega}{2\rho} \right)^{\frac{1}{2}}z [/tex]
yungman said:I see, that makes the whole world of sense! I was going in circle as I use ρ as charge!
Thanks
Yes, aluminum can experience eddy currents when exposed to varying magnetic fields. This is because aluminum is a conductive material, and when a varying magnetic field passes through it, it induces a current in the metal, known as an eddy current.
Eddy currents can cause heating in aluminum due to the resistance of the metal. This can result in energy loss and potential damage to the material if the currents are strong enough. Eddy currents can also create magnetic fields that oppose the original magnetic field, which can cause changes in the overall magnetic field.
There are several ways to minimize eddy currents in aluminum, such as using laminated sheets of aluminum or adding a non-conductive coating to the surface. These methods can help reduce the flow of eddy currents and minimize any negative effects.
Yes, eddy currents in aluminum can be beneficial in certain applications. For example, they are used in induction heating processes, where the heat generated by the eddy currents is used to melt or heat metals. Eddy currents can also be used in non-destructive testing methods to detect flaws or defects in aluminum materials.
The thickness of the aluminum can affect the strength and magnitude of the eddy currents induced by a varying magnetic field. Thicker aluminum will have a higher resistance, resulting in stronger eddy currents and potentially more significant effects. On the other hand, thinner aluminum may have lower resistance and weaker eddy currents. However, the shape and conductivity of the aluminum also play a role in the strength of eddy currents.