Hi Richard, TOP and internal posting...sorry folks.

I think you are learned on this subject and won't quibble about what
really happens in the real world. I think you know and I claim that I know.
I will, however pick a little bone in regards to the answer which I
posted to an email since I also thought would help others at a similar level
of understanding or confusion.

Oh geeze! here he goes...you had to set him off..
Here's my mantra and why a I am a little miffed by (but actually understand)
frequent attempts to correct my explanations.
The words we use and the depth to which we go at any given point to
describe things, have an effect on the ability of people to absorb the
concepts. As an instructor of basics, I have worked very hard, for a long
time, to understand and use effective ways to transfer an understanding of
electronic principles to students at what might be considered the lower
rungs of the technical ladder...the beginners...the hams also. There is
what I'll call an "instructor's high" associated with the light bulb going
on in a student. It's really cool.
I carefully craft my responses to the apparent level of knowledge of the
questioner. I do my best to form a coherent story which progresses from
simple, where a concept needed to understand more complex concepts is
explained first, without adding the unnecessary complications of true, but
potentially confusing facts, to the more complex goal I perceive to be the
questioner's goal. Once the basic concepts sinks in AND the student is
ready for the next level, usually by a response, I then proceed to build. It
is the old "speak to your audience" concept.
I don't dispute that your explanations are correct. They appear very
good, rather complete. I do believe however, that your most assuredly
honest and well meaning attempt to be correct, completely correct, actually
makes the subject more confusing to the beginner. I believe this because I
have been there. In fact, I must, almost every class session, throttle
myself from doing just the very same thing. Why? Because when I do, I have
succeeded in causing more confusion, resulting in a mental block to learning
which requires much more effort at damage control to erase the mental
blockage I created with my ignorant desire to be completely correct. Please
understand that I am being harsh on *myself* because I have been frustrated
by this and work hard to keep it under control. As an Engineer, teaching
technician students, one must keep in mind that there is a different state
of mind and ability to absorb what to them, appears a very complex
subject...but to my arrogant mind is really very simple. After all,
piecewise parametric polynomial interpolation looked like an impossible
concept, way beyond my comprehension back in 92 when I first saw reference
to it. Now, it looks like the simplest thing any high school Algebra
student can understand.

I'm also at a point in my life that I have seen and done so much in
this field (and it all seems so simple) that I wish to return some of it to
others, and I wish to do it very effectively.

Of course, now you're going to tell me that you also have been teaching for
x years and your methods are equally successful...so be it. There needs to
me more of us.

BTW...what is your line, Richard?

Some comments, corrections and whatever stuck my fancy about what you
wrote...


"Richard Harrison" wrote in message
...
Steve Nosko wrote:
"Apparently, because of the way the big bang occurred, when we put a
voltage across a resistor current flows in a manner that we discovered
follows the equation called Ohm`s law."

Big bang? Ohm wasn`t around then. He lived 1787 to 1854. Ohm discovered
that current in an electrical resistance is proportional to voltage.

The concept I was trying to relate in a slightly 'light' manner was:
The stuff that happens, happens 'cuz of what we call "physics",
"physical laws" or "nature" or sump-in' like that, not because there is an
equation making it happen. Resistors don't know Ohm's law and don't conduct
current because of Ohm or his discoveries.

The equation we call Ohm's law is simply a model of how reality works.
Like a model airplane, which helps us understand what a real airplane looks
like. Ohms law, and all the other equations, help us understand what real
electronics "looks like".


Resistance is the type of impedance (opposition to electrical current)
in which current is locked in step to the applied voltage.

A completely valid way to word it, but to a beginner I think the phrase
"locked in step " is vague. It would be a good start, but probably needs
expansion to explain what it means.



The item called a resistor is the type of resistance that converts
electrical energy to heat energy.
Not all resistances are resistors.

I wouldn't have worded it that way, but it (resistor is the type of
resistance) is a valid model to have in mind. That is, as a way to
distinguish it from "a resistance which is not a resistor". This made me
think of how I think of it.. and when I use the word "resistance" I think of
it as as a resistor, yet an impedance has a real or "resistive" part. That
word "resistance" for me conotes a "resistor" where the others conote the
other concept. Interesting nomenclature, that's all.

Some resistances don`t convert
electrical energy directly into heat. In these non-dissipative
resistances,

Well, here's where I'll say that I think this is truly a matter of
symantics. Your terminlolgy implies that dissipation = heat. I agree that
the most common usage it that "... is dissipated as heat...". However, this
next bit:
...is in-phase with current through the
resistance, but it does not cause energy loss.

I think has a symantics problem. I'm sure you truly understand what
happens, but the words "...does not cause energy loss." isn't correct,
because the energy IS lost from the circuit. The circuit "can't tell" the
difference 'tween the resistor and any other kind of resistive component.
It just may or may not be as heat, right?
You know what happens and I know what happens, but the OP didn't, so
I was starting him down a path that wouldn't paint him into a corner of not
being able to understand the other resistive types of things later...if so
desired.


An example of lossless
resistance is the Zo or surge impedance of a transmission line.

Again, the power IS lost from the source, no? I think this an important
basic understanding. To the sourse, it is gone. Poof! never to be seen
again. I think it is a good model to understand and helps go further
without Maxwell complicating things. I think you can go pretty far without
Maxwell (gee, twice in one paragraph) and still have a good amount of
(correct) sixth sense about what is going on in electronics and transmission
lines.


Zo is ... yet converts no energy to heat in the lossless line.

And my model didn't exclude this. I thought I was explicit about
that without bringing in more complexity for the OP.


"radiation resistance". ...is hardly a loss.

Again, as far as the transmitter circuitry is concerned, it is.


The following is a well done explanation which goes further and into
more detail...with one disagreement.

An ohm is the unit of resistance. It is defined at 0-degrees C, of a
uniform column of mercury 106.300 cm long and weighing 14.451 grams. One
ohm is the resistance which drops one voltt when a current of one amp is
passed through it.

Reactances are also defined by their volts to amps ratios (ohms). The
big difference is that reactance does no work and produces no heat.
Opposition to electrical current comes from delay required to store ard
retrieve energy to and from fields in and around the reactances. Current
lags the applied voltage in an inductance. At time = 0, no current flows
into an inductance, but rises exponentially from the instant of initial
energization. Current leads the applied voltage into a capacitance. At
time = 0, full current flows into a capacitance but voltage across the
capacitance is zero and rises exponentially from the instant of initial
energization.

In an a-c circuit, the current through an inductance lags the voltage by
90-degrees. In a a-c circuit, the current through a capacitance leads
the voltage by 90-degrees. Phase shifts are produced by energy storage
in reactance. There is no phase shift in a resistance. No electrical
energy is stored in a resistor, but its matter does have a thermal
capacity. Once its atoms are agitated by heat their inertia is evident
in the resistance`s temperature. It takes time to cool.

Steve wrote: "Things get all messed up."

As old Carson Robinson sang: "Life gets tedious, Don`t it?" Steve gave
the formulas for capacitive and inductive reactances. They have always
seemed convenient to me. Steve says: "---we call this new kind of
(corrupted) resistance "Impedance"."

No. Impedance is the general name for opposition to electricity.

No. In the context of my writing for someone who has an unserstanding
of DC and resistance, reactance it a very confusing factor. It corrupts an
otherwise simple world. Getting into Vector Algebra and phasors is a
significant step up in mathematics for the beginner not inclined to go the
Engineering route. What I'm saying is that although the unified field
theory may very well be the absolutely correct explanation of everything in
the universe, we don't need to explain it fully in the beginning to help
someone understand Gravity's acceleration, F=MA and you can't push a rope.
Newton certainly didn't need it. For all I know, F=MA may very well be a
special case in quantum mechanics, but I don't need it to calculate
accelerations, velocities, etc


Resistance is the specialized name for the case in which the impedance
alone causes no delay and stores no electrical energy. All electrical
impedance is defined by its voltage to current ratio, and is the total
opposition (resistance and reactance) a circuit offers to the flow of
electricity. For d-c, reactance doesn`t count. For a-c, total opposition
consists of the vector (phasor) sum of resistance and reactance in a
circuit. Impedance is measured in ohms and its reciprocal is called
admittance. The symbol for impedance is Z. The symbol for admittance is
Y.

Steve also writes:
"Poof! BUT converts it into radio frequency energy (RF) also called an
electromagnetic field or wave."

Yes. A radio wave is r-f energy which has escaped the confines of wires
and doesn`t come back. Whenever wires in open space carry high-frequency
current, some energy gets away as a radiated field, having a strength
that varies inversely with the distance.

Best regards, Richard Harrison, KB5WZI