Antonio Vernucci wrote:
- an ideal electrical engine (no ohmic loss, no friction) fully
transforming the applied electrical power into mechanical power. It
looks like a resistor, but no heat is generated anywhere

No, it looks like a resistance, not a resistor. There is one
IEEE definition for resistor. There are two IEEE definitions
for resistance. A resistor with current dissipates power. A
resistance may or may not dissipate power. One definition of
resistance in the IEEE describes a dissipationless resistance.
There is no such thing as a dissipationless resistor.
--
73, Cecil http://www.w5dxp.com

- an ideal electrical engine (no ohmic loss, no friction) fully
transforming the applied electrical power into mechanical power. It looks
like a resistor, but no heat is generated anywhere

No, it looks like a resistance, not a resistor. There is one
IEEE definition for resistor. There are two IEEE definitions
for resistance. A resistor with current dissipates power. A
resistance may or may not dissipate power. One definition of
resistance in the IEEE describes a dissipationless resistance.
There is no such thing as a dissipationless resistor.

It IS a resistance, but it LOOKS like a resistor because, from the exterior, one
has no means to determine whether energy gets dissipated or transformed in some
other form.

73

Tony I0JX

Antonio Vernucci wrote:
It IS a resistance, but it LOOKS like a resistor because, from the
exterior, one has no means to determine whether energy gets dissipated
or transformed in some other form.

Appearances can be deceiving. It doesn't look
like a resistor to me until I hold it in my hand.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
There is no such thing as a dissipationless resistor.
--
73, Cecil http://www.w5dxp.com

Andy comments:

Not to make too fine a point on this, Cec, but I , personally,
would consider a perfect 52 ohm antenna to be a dissipationless
resistor......... although, in the cosmic sense, the power that is
fed into it will eventually reside as "heat" in the bowels of the
cosmos.....somewhere......

Actually, .... "heat" is simply EM at a different frequency....
..... Hmmmmm... I see a deep, philosophical discussion brewing
here..... ..

... Me brain hoits......!!!!

Andy W4OAH

On 1 Apr 2007 09:16:46 -0700, "AndyS" wrote:

I see a deep, philosophical discussion brewing
here....

Only if it starts out with:
"Who's on first?"

AndyS wrote:
Not to make too fine a point on this, Cec, but I , personally,
would consider a perfect 52 ohm antenna to be a dissipationless
resistor......... although, in the cosmic sense, the power that is
fed into it will eventually reside as "heat" in the bowels of the
cosmos.....somewhere......

Yep, a common misconception. The feedpoint impedance
of a standing-wave antenna, like a 1/2WL dipole, is
a *virtual* impedance equal to (Vfor+Vref)/(Ifor+Iref).
It may be a resistance, but it is not a resistor. It
is essentially the same entity as the impedance looking
into a stub. For a resonant 1/2WL dipole the equation
becomes:

Feedpoint resistance = (|Vfor|-|Vref|)/(|Ifor|+|Iref|)

With Vfor at a reference angle of zero, Vref is at
180 degrees. With Ifor at zero degrees, Iref is
also at zero degrees. Thus the ability to add and
subtract magnitudes directly.

Some guru once challenged me to make a measurement
at the shack and tell the difference between a 50 ohm
dipole and a 50 ohm resistor. Told him all I needed
was a field strength meter. :-)

The words "impedor" and "resistor" are reserved for
real physical devices. The words "impedance" and
"resistance" have two meanings and can mean either
real devices or virtual V/I's. So says the IEEE
Dictionary.
--
73, Cecil http://www.w5dxp.com

On Sun, 01 Apr 2007 18:24:33 GMT, Cecil Moore wrote:

AndyS wrote:
Not to make too fine a point on this, Cec, but I , personally,
would consider a perfect 52 ohm antenna to be a dissipationless
resistor......... although, in the cosmic sense, the power that is
fed into it will eventually reside as "heat" in the bowels of the
cosmos.....somewhere......

Yep, a common misconception. The feedpoint impedance
of a standing-wave antenna, like a 1/2WL dipole, is
a *virtual* impedance equal to (Vfor+Vref)/(Ifor+Iref).
It may be a resistance, but it is not a resistor. It
is essentially the same entity as the impedance looking
into a stub. For a resonant 1/2WL dipole the equation
becomes:

Feedpoint resistance = (|Vfor|-|Vref|)/(|Ifor|+|Iref|)

With Vfor at a reference angle of zero, Vref is at
180 degrees. With Ifor at zero degrees, Iref is
also at zero degrees. Thus the ability to add and
subtract magnitudes directly.

Some guru once challenged me to make a measurement
at the shack and tell the difference between a 50 ohm
dipole and a 50 ohm resistor. Told him all I needed
was a field strength meter. :-)

The words "impedor" and "resistor" are reserved for
real physical devices. The words "impedance" and
"resistance" have two meanings and can mean either
real devices or virtual V/I's. So says the IEEE
Dictionary.


Amen to that, Cecil

Walt, W2DU