[SI-LIST] Re: Direction of displacement curent
- From: Mervin J <mervin.jacob@xxxxxxxxxxx>
- To: Long Yang <long.0.yang@xxxxxxxxx>
- Date: Tue, 13 Mar 2012 18:34:49 +0530
Its true. But the physical meaning of this displacement current is that
a changing electric field makes a changing magnetic field. To find the
direction of the magnetic field produced by this effect we can use
right-hand rule for currents. In other case if the electric field is
decreasing in time, then the negative time derivative gives a
displacement vector that points opposite to E.
On 3/13/2012 1:28 PM, Long Yang wrote:
> Displacement current is not an electric current of moving charges, but
> an electric field that varies with time.
> For perfect PCB traces, energy propagates in the way of
> electromagnetic wave.
> The trace plays the role of wave guide, not current conduit.
>
> When TEM mode dominates, electric field is from ground to trace (and
> reversed along propagation).
> This is also the direction of displacement current, flowing by the way
> of capacitance between gnd and driven signal.
>
> On Mon, Mar 12, 2012 at 22:21, Mervin J <mervin.jacob@xxxxxxxxxxx
> <mailto:mervin.jacob@xxxxxxxxxxx>> wrote:
>
> As per Maxwell's equation, The direction of displacement current is
> along the conduction current.
>
>
> On 3/13/2012 6:54 AM, Long Yang wrote:
> > In Maxwell's equations, there are two items about current,
> conduction
> > current and displacement current.
> > Conduction current is sometimes expressed related to electric
> field by
> > conductivity.
> > In the similar way, you can expect that displacement current has the
> > similar relationship with electric field.
> >
> > Regarding PCB trace, the electric field inside copper trace is
> driven by
> > driven voltage potential, so conduction current is along the
> copper wire.
> > While the electric field of TEM mode is from signal trace to
> ground, and
> > that implies the direction of displacement current.
> >
> > thanks
> >
> > On Mon, Mar 12, 2012 at 11:31, Antonis
> Orphanou<orphanou@xxxxxxxxxxxx <mailto:orphanou@xxxxxxxxxxxx>>wrote:
> >
> >> On displacement current:
> >> If you assume that for all the copper surfaces the tangential
> electric
> >> field is zero and that there is only a normal E-field component
> (which
> >> gives rise to the copper surface charge density) then you could
> visualize
> >> the displacement current. It is the time derivative of the
> E-field in that
> >> same direction.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>
> [mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>]
> >> On Behalf Of Aaditya Kandibanda
> >> Sent: Sunday, March 11, 2012 8:36 PM
> >> To: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
> >> Subject: [SI-LIST] Direction of displacement curent
> >>
> >> Hello everyone,
> >> Can you please let me know what will be the direction of
> displacement
> >> current on the traces of PCB, I am trying to understand it for
> analysis of
> >> near and far end cross talk on PCB traces. the problem is, when
> there is a
> >> equal distribution of capacitance along the length of 2 PCB
> traces? what
> >> will be the direction of displacement current? If possible can
> some one
> >> briefly let me know about the near end and far end cross talk?
> I am trying
> >> to understand it, I see different authors express it in
> different views
> >> which is confusing me as a novice.
> >>
> >>
> >> Thanks and regards
> >> Aaditya
> >>
> >>
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