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Old 14th January 2013, 05:15 PM   #32661
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Something in relationship with the moon's position in this fighting club or just temporary shortage of peanuts ?
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Old 14th January 2013, 05:43 PM   #32662
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Something in relationship with the moon's position in this fighting club or just temporary shortage of peanuts ?
I vote for the peanut shortage . Their moms must have sent them out for more . After they return from the store go down the stairs in to the basement the show will continue . This is just intermission .
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Old 14th January 2013, 06:00 PM   #32663
DF96 is offline DF96  England
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Originally Posted by scott wurcer
If absolute value is bothersome I think in the solution you will find some square-root of quantities squared which has the same effect as taking the absolute value.
I have just had a quick look at two textbooks. I can't see anything in the maths of skin effect which involves either squares of field quantities or squares of square roots. The geometric field distribution is a function of just frequency, then multiplied by the field strength at the surface. So if you double the surface field, you get exactly the same pattern but everywhere the field is doubled. The linearity of Maxwell's equations require this to be true.

As proximity effect is just the mutual version of skin effect I would expect the same there.

Now if the Lorenz force is moving conductors around then 2nd harmonic is quite possible. That may be what is happening.
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Old 14th January 2013, 06:34 PM   #32664
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I have just had a quick look at two textbooks. I can't see anything in the maths of skin effect which involves either squares of field quantities or squares of square roots. The geometric field distribution is a function of just frequency, then multiplied by the field strength at the surface. So if you double the surface field, you get exactly the same pattern but everywhere the field is doubled. The linearity of Maxwell's equations require this to be true.

As proximity effect is just the mutual version of skin effect I would expect the same there.

Now if the Lorenz force is moving conductors around then 2nd harmonic is quite possible. That may be what is happening.

Certainly the energy lost from heat from the (very) slight change in resistive loss at twice per cycle is always positive. In fact the change in real part of the resistance is the only thing that could matter in this case.
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Old 14th January 2013, 06:46 PM   #32665
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Originally Posted by scott wurcer
Certainly the energy lost from heat from the (very) slight change in resistive loss at twice per cycle is always positive.
Yes of course.

Jn is claiming more than that: he says that the current flow geometry changes too with signal level. That is what I dispute.
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Old 14th January 2013, 07:25 PM   #32666
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Yes of course.

Jn is claiming more than that: he says that the current flow geometry changes too with signal level. That is what I dispute.
No, I did not say that. It is important you be clear on that.

The effect is slew rate dependent. The current density modification is directly proportional to the currents induced within the conductive material. The currents are directly proportional to the induced voltage ala Faraday's law of induction.

The resistance increase is a function of the absolute value of the rate of change of the current within the wire which is creating the magnetic field. That is why Ed sees the second harmonic.

jn
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Old 14th January 2013, 07:37 PM   #32667
DF96 is offline DF96  England
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Slew rate derives from two parameters: frequency and amplitude. You are attaching significance to the latter. The theory attaches significance to the former.
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Old 14th January 2013, 07:53 PM   #32668
RNMarsh is offline RNMarsh  United States
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Slew rate derives from two parameters: frequency and amplitude. You are attaching significance to the latter. The theory attaches significance to the former.
.... because 'rate' doesnt change by amplitute.
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Old 14th January 2013, 08:10 PM   #32669
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.... because 'rate' doesnt change by amplitute.
Yes from the amplifier point of view when driven by step.

But for sine wave, slew rate (derivative at zero) is amplitude times frequency times 2pi.
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Old 14th January 2013, 09:14 PM   #32670
RNMarsh is offline RNMarsh  United States
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Yes from the amplifier point of view when driven by step.

But for sine wave, slew rate (derivative at zero) is amplitude times frequency times 2pi.
yes, there is Slew rate, too. For amplifiers. Physics or amps? What's the focus here? -RNM

Last edited by RNMarsh; 14th January 2013 at 09:21 PM.
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