# [SI-LIST] Re: Direction of displacement curent

• From: Long Yang <long.0.yang@xxxxxxxxx>
• Date: Mon, 12 Mar 2012 18:24:20 -0700

```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>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]
> On Behalf Of Aaditya Kandibanda
> Sent: Sunday, March 11, 2012 8:36 PM
> To: 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
>
>
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