John Popelish wrote:
Cecil Moore wrote:
John Popelish wrote:

At any point along the wire, and at any particular instant, whether
as a result of a standing or traveling wave, the current flows in the
direction of the wire, one way or the other. Such current does not
have a phase. It has a direction.


In what direction is the RMS value of standing wave current flowing?

That's easy. RMS current is an AC measurement of current along the
conductor. Over any integer number of cycles, the total movement of
charge is zero. The current spends half the time going one way, and
half the time going the other way. This applies to both standing and
traveling wave induced currents. The only current that describes a net
movement of charge in a single direction is DC.

I see that Cecil is still having trouble with RMS, as well as with
current. Otherwise he couldn't have come up with the nonsense question

In what direction is the RMS value of standing wave current flowing?

The RMS value of current doesn't flow. Charge flows, and current is the
rate at which it flows. RMS is one way of expressing the magnitude of a
time-varying current. In a steady state environment of pure sinusoidal
waveforms, any current can be expressed as Ipk * cos(wt + phi) where Ipk
is the peak value of the current, w (omega) is the rotational frequency,
and phi is the phase angle. This gives you precisely the value of
current at any instant in time, t. You can equally well express it as
Irms * cos(wt + phi) where Irms is the RMS value of the current. Nothing
is lost or gained by choosing one convention or the other, and using RMS
doesn't require abandoning the time varying or phase information. (In
EZNEC I chose to use RMS; NEC uses peak. They differ only by a constant
factor of the square root of 2. Both report phase angle along with
amplitude.) In either case, if you know or assume w, the current at any
instant is known if you know phi and either Ipk or Irms.

A point of clarification to John's posting:

When a standing wave exists on a transmission line, the phase of the
voltage or current is fixed (other than periodic phase reversals) with
position only if the end of the line is open or short circuited.
Otherwise, the phase of voltage and current will change with position.

Roy Lewallen, W7EL