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# Re: [femm] Re: Current

- To: femm@yahoogroups.com
- Subject: Re: [femm] Re: Current
- From: David Meeker <dmeeker@ieee.org>
- Date: Tue, 23 Jul 2002 09:49:14 -0400
- References: <ahgh7h+q70o@eGroups.com> <5.1.0.14.0.20020723080648.00aa9230@staff-mailin.lboro.ac.uk>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.0.0) Gecko/20020530

`Keith Gregory wrote:`

> `At 20:29 22/07/2002 -0400, you wrote:`

> > `brian_hawes wrote:`

> > >     Keith,
> > >     Thanks for the reply. My problem is thus: I have a simple simulation
> > >     of a single curent carrying ring. I have defined the current density
> > >     in the model for the copper. If I simulate at very low frequency,
> > >     such that skin and proximity effects are negligable, then the total
> > >     current, found by using the block integral feature in FemView, is
> > >     what I would expect - J x Area. Now, if I increase the frequency such
> > >     that skin and proximity effects occurr, then the total current,
> > >     measured with FemView appears to fall. I would expect, as you say,
> > >     that the total current would remain constant, and just be
> > >     redistributed.
> > >     Brian

> > `
> > If you define a "source current density," this is defines the current that you would get at 0 Hz. At nonzero frequencies, in conductive regions, some of the current gets bucked by inductance.`

> ``
> `I think I had begun to work this out looking at a similar situation to that Brian has been using. The current density seems to act in a manner similar to what would occur if a constant voltage was applied to the region rather than a constant current. Am I on the right track or is it not this simple?`
> `Keith.`

`
Yes, that's right--the current density that you assign is a "source current density" which would be the same as conductivity*voltage gradient (at least for regions with a nonzero conductivity...) To force a particular net current on a conductive region regardless of frequency, you have to use the "circuit" properties to do it.`
`Dave.`
``

- Follow-Ups:
  - Re: [femm] Re: Current
    - From: Keith Gregory <k.gregory@lboro.ac.uk>

- References:
  - Re: Current
    - From: "brian_hawes" <b.hawes1@physics.ox.ac.uk>
  - Re: [femm] Re: Current
    - From: Keith Gregory <k.gregory@lboro.ac.uk>

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