[Prev][Next][Index][Thread]
Re: Displacement Current Revisited
Sooo, let me get this straight;
Current density is just the current / volume of space?
But that should be calculated from the number of winds
per unit volume N(0); if that's all it is.
Unless we are discussing the effective stored EM energy
of the magnetic field that has an equivalent effect to
an actual current, which is what I was referring to.
Bryan Kaufman
Tesla List wrote:
>
> Original Poster: "John H. Couture" <COUTUREJH-at-worldnet.att-dot-net>
>
> Bryan -
>
> My understandung of displacement currents is that they refer to current
> density which is not the same as the currents we are measuring with an
> ammeter. To my knowledge no one has ever measured a displacement current or
> even suggested how to measure these currents around a Tesla coil. How about
> a fluorescent lamp? Apparently displacement currents are only one possible
> method to describe electromagnetic fields using a density or unit volume as
> a way to describe a quantity of electrical charges moving thru space.
>
> I don't think "the equation implies phase shifted Id coaxial to I(real)"
> because the Id is in the form of current density and the I(real) is in the
> form of current intensity. The standard ammeter measures current intensity.
> How would you measure current density around a TC except by knowing the
> volume of a container such as a fluorescent lamp?
>
> John Couture
>
> --------------------------
>
> At 02:51 PM 3/20/99 -0700, you wrote:
> >Original Poster: Bryan Work <bryan-at-apexrad-dot-com>
> >
> >John,
> >
> >Personally, I find this discussion very relevant; but then again
> >I'm not the EE type this list seems well populated by.
> >
> >I was actually looking for the Id equation, myself; Thank You
> >
> >If I am applying the concept correctly, (no guarantee of that)
> >the equation implies phase shifted Id coaxial to I(real).
> >
> >However, dE/dt is max as E crosses zero.
> >So I and Id are coherent.
> >However this applies only to the inductor,
> >in the situation of the TC toroid there must be (IMHO)
> >a longitudinal Id to ground plane as well as a radial
> >Id from space charge.
> >
> >But the only one that would
> >conceivably not have a coherent I(real)
> >would be the last one.
> >Does anybody know if this is where
> >free air streamers arise from?
> >Or am I just oversimplifying?
> >
> >Bryan Kaufman
> >
> >Tesla List wrote:
> >
> >> Original Poster: "John H. Couture" <COUTUREJH-at-worldnet.att-dot-net>
> >>
> >> Greg, Terry, All -
> >>
> >> Nothing apparently has happened to the notion that "displacement"
currents
> >> are still considered to be caused by the changing E field. Cook gives the
> >> equation:
> >>
> >> Id = (eo)(dE/dt)
> >>
> >> Id = Displacement current density
> >> (eo)(dE/dt) = per Maxwell's equations
> >>
> ------------------------- snip