two mistakes in Tutorial no. 14

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uwestoehr
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two mistakes in Tutorial no. 14

Post by uwestoehr »

In the Tutorial no. 14 "Magnetic field induced by harmonic current in a wire" are two bugs:

1. Equation 14.3 states how to calculate B for a given wire radius. In the Text it is written that R is 0.01m, but to get the mentioned result of B = 0.037T, the radius R is 0.001 m.

Looking at the grid of the wire (wire.grd), this must be correct, because to get a field strength of 1 V/m at the given U = 0.01V, the wire must have a length of 10 mm and the wire is longer than its radius.

So just a simple typo, but it was confusing for me. I hope this can be fixed.

2. When performing the tutorial to its end one gets as result a maximal imaginary B of 0.052 T (while Re(B) = 0.011). In the tutorial text, it is written that Im(B) would be 0.524 T. This would be a factor 10 too high. So I think also here there I think the fix is to correct the tutorial text.
Rich_B
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Joined: 24 Aug 2009, 20:18

Re: two mistakes in Tutorial no. 14

Post by Rich_B »

Good catch! Something to include in the next update for the tutorials.

Thanks, Rich.
uwestoehr
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Re: two mistakes in Tutorial no. 14

Post by uwestoehr »

Rich_B wrote: 09 Feb 2023, 23:23 Good catch! Something to include in the next update for the tutorials.
I downloaded the latest tutorial from February 9th. The mentioned issued have not yet been fixed. I could do this but don't know where to submit a PR for the docs.
Rich_B
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Joined: 24 Aug 2009, 20:18

Re: two mistakes in Tutorial no. 14

Post by Rich_B »

Hello Uwe,

I'm working on fixing the tutorial.

Point 1, yes, the radius should be 1 millimeter, 0.001 meters.

Point 2, I'm coming up with an imaginary B of 0.0052 T. I added a Saveline solver, and that's the result at the surface of the wire at radius = 0.001 meters.

Some of the manuals (including the tutorials) are available on Github:

viewtopic.php?t=7207

Rich.
Rich_B
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Joined: 24 Aug 2009, 20:18

Re: two mistakes in Tutorial no. 14

Post by Rich_B »

Attached is the ElmerGUI project, with the Saveline solver addition.

The included csv file has the saveline results, plot ' 4: coordinate 1' versus ' 19: magnetic flux density im 2' for the result.

I've seen that Paraview can also generate a line result, but don't know how to actually do that. It would be interesting to compare the two methods.

Rich.
Attachments
MagneticFieldWire-100khzSaveline.zip
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uwestoehr
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Re: two mistakes in Tutorial no. 14

Post by uwestoehr »

Rich_B wrote: 13 Feb 2023, 16:15 Point 2, I'm coming up with an imaginary B of 0.0052 T. I added a Saveline solver, and that's the result at the surface of the wire at radius = 0.001 meters.
Hi Rich, sorry for the late reply, but the forum does not send me any notifications despite I enabled them.

To the issue number 2:
you get 0.0052, I get 0.052, the tutorial states one should get 0.524, so there is definitely a bug.
You get 0.052 because you set

Code: Select all

AV re = 0.01
my mistake was that I set

Code: Select all

AV re = 0.1
So the correct value is yours: 0.0052 and the tutorial manual has to be corrected accordingly.
Rich_B
Posts: 421
Joined: 24 Aug 2009, 20:18

Re: two mistakes in Tutorial no. 14

Post by Rich_B »

Hello Uwe,

Now that our results agree, I'll take care of updating the tutorial manual.

The forum doesn't send notifications, and hasn't for several years. One tactic is to create a bookmark in your browser to your own forum post, and every day or so, click on the bookmark to check for answers.

Thanks, Rich.
uwestoehr
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Re: two mistakes in Tutorial no. 14

Post by uwestoehr »

Rich_B wrote: 18 Mar 2023, 17:00 The forum doesn't send notifications, and hasn't for several years.
Can this please be fixed? We use phpBB for FreeCAD and it can send emails.

For example, I could not login, tried to change my password, but since the forum does not send any emails, one cannot change the password once one has it forgotten.
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