From: snarfy@cruzio.santa-cruz.ca.us
Newsgroups: sci.physics
Subject: Instant Communications
Keywords: Snarfy , from the Kirchoff's Law Enforcement team
Date: 31 Jul 92 08:41:27 GMT
Reply-To: snarfy@cruzio.santa-cruz.ca.us



  ____     _     __   __       ?    ``The sum of the currents  flowing into
 <___ /\  / \   /__\ /__ \__/ /|\     a junction is equal to the sum of the
 ___//  \/ --\ /  \ /      / / | \    currents flowing out of the junction.''
[_________________________/ /  |  \   -Gustav Kirchoff (1824-1887)

 (..netcom!cruzio!snarfy)

    J A Carr writes:

>  Your warm food has more momentum and energy (in the thermal  motion)  that
> it gained by absorbing the microwave photons energy and momentum.

    Snarfy responds:
  Ok  professor  ,  I  think  I  understand now.  By your definition a mass is
  independent of it's temperature. I've monitored  a   discussion of  this  by
  others  on  the  net and I'll quote it here. I believe this involved McIrvin
  and Palmer:

  Reference   article   <mcirvin.711904014@husc8>    mcirvin@husc8.harvard.edu
  (Mcirvin)

  palmer@sfu.ca (Leigh Palmer) writes:

>>>> "Mass" as you use it
>>>>is equal to neither inertial nor gravitational mass as those terms apply to
>>>>any system more complicated than a particle at rest!

  Mc:
>>>Which only illustrates that those concepts are only really useful in
>>>the context of Newtonian physics, IMHO.

  P:
>>To further confuse the
>>beginning physics student you could explain that the mass of that lump of
>>matter is independent of its temperature.

  Mc:
>>Actually, neither definition of mass would be temperature-independent,
>>if you define it for the whole lump of coal.  When you raise the
>>temperature, the energy in the rest frame increases!  The sum of
>>the masses of all the particles is perhaps temperature-independent,
>>but as you complained before, that's not the mass of the lump.

  P:
>Exactly my point!
  --------------------------------------------------------------------
    Snarfy to Carr 7/30 :

       I  once accused you of preferring to confuse people.  Perhaps you
       don't *prefer* to do so , but I  hope  you  understand  from  the
       above  that  we  hadn't  postulated  mass  being  independent  of
       temperature during the  ``inquisition''  hearing  (I'm  glad  you
       found  it amusing) therefore hadn't defined our terms yet- so the
       result was confusion on my part.

  Anyway ,now that we understand each other,see Kirschoff's law (Header quote
  above)

  Rephrasing: At a junction: I(in) = I(out)

  I hope we don't have to add qualifiers to this one!

  Before proceeding let's deal with Ben Weiner's arguments:

       Throughout  this  discussion  I'll   use   Beiser's   ``Physics''
       (Cumming's  Publishing,  1973  edition  as  a reference.  Numbers
       after assertions indicate page numbers from this volume. Formulas
       for  impedance  are  from  David  Leithauser's   ``Programs   for
       Elecronic Circuit Design''(1986) Radio Shack

>C'mon Snarfy, Ohm's law doesn't apply to everything in the world.
>It doesn't even apply to lightbulbs (non-ohmic devices).

       The  only qualifier for Ohm's law is where the ratio V/I is NOT a
       constant and is dependent on the values of V and  I.  (p.429)  In
       the  case  of  a lightbulb the R value of tungsten is temperature
       dependent(p.430). Therefore the ohms value that you measure  with
       an  ohmmeter , imposing a V of millivolts on the filament to make
       the measurement, is different than the ohms  value  derived  when
       it's operating V is applied (say 120 volts). Nevertheless ,if you
       measure  the  current  at  the  rated voltage ,the resistance (R)
       value is still calculated as =  V/I.  (derived  from  example  on
       p.430)

> More to  the point, derivations of Ohm's law tend to assume a  quasi-static
> uniform  E-field (driving voltage).

       On the contrary. AC impedances are evaluated in terms of ohms (p.
       585).   It's a matter of I (Rate of energy transfer) = V (Force)/
       z (impediment to Force) at any given instant in time. Since an AC
       voltage  isn't  constant ,V(effective) = V(max)/sqrt 2 or .707 of
       V(max) (p.576). After V(eff) is derived this value can be plugged
       into ohms law to determine I(eff) given a known R or z.

        Electromagnetic  ``waves'' are not really waves, but positive to
       negative variations of V amplitude which take place over  periods
       of  time  and  at  a  given  location,  usually  from a line like
       radiating source  element  called  an  antenna  (no  reference  ,
       snarfy's  dictum).  These  variations simply LOOK like waves when
       translated to voltage/time coordinates on an oscilloscope (I hope
       this is obvious).  AC  Impedances  are  really  derivations  from
       applied  voltage  and resulting current just as in static fields.
       Certainly, I and R values are frequency dependent for  any  given
       value of L (Inductance) and C (Capacitance), but you still end up
       with I = V/z (z evaluated in ohms).

>  If  you  change  the  resistance  there  will  still  be  a  delay  as  the
> changing E-field propagates through your system at the usual speed: that of
> light.

        The  V(eff)  of  E  field doesn't change except at the receiving
       element which may be only a few inches/ feet / meters  (whatever)
       in length.  Were not concerned with propogation speeds inside the
       receiving element.  As far as the SYSTEM (receiver - transmitter)
       is  concerned ,the E field may diminish as it propagates (perhaps
       according to the inverse square law, perhaps not as in  the  case
       of a collimated or coherent beam) but it can remain at a constant
       value  as  measured  from any given point between transmitter and
       receiver.   Transfer  of  information  is  not  performed  by   a
       variation  of  the  E ( V(eff) )  field  as  in carrier amplitude
       modulation .  We vary current draw by varying the  inductance  or
       capacitance  of  the  recieving  element.  A variation of current
       draw may have an effect on the receiver's *  LOCAL*  E ( V(eff) )
       field, but this need not be detected at the transmitter site.


> By  the  way,  don't forget the effects of inductance, possible capacitative
> resonances, and variable impedance thingies like wet trees in your broadcast
> circuit.

       We  will  assume a resonant tuned circuit to be the ideal , we've
       discussed  inductance  ,and  we'll  steer  our  beam   clear   of
       ``thingies''.


        Now  , back to current draw.  Again, Kirschoff's law states that
       at a junction I(in) = I(out)  .   Since  a  junction  is  usually
       considered  to  be  a  place  where three conducting elements are
       joined , consider a system of a transmitter 18.63  miles  distant
       from  two  receiving  antennas  .   At  resonance , the receiving
       antennas each ``drain'' 1/10  of  the  available  output  of  the
       transmiter. The rest of the transmitter's energy is ``wasted'' on
       heating  the atmosphere or distant intergalactic nebulas.  If one
       of the antennas is suddenly oriented away from  the  transmitter,
       the  same  mass  still  stands  between  the  transmitter and the
       distant galactic nebula and the atmosphere  beyond  the  antenna.
       The  entire  resonant  system is now detuned ,however, because of
       the effective removal of one of the inductive elements  from  the
       system.   If  the effect of this detuning took the time necessary
       for light  to  traverse  the  18.63  miles  to  register  at  the
       transmitter,  then  you  would have a violation of Kirchoff's law
       which  endures  for  .1  milliseconds  (  a  virtual  eternity  ,
       leptonically speaking).

        What  more can a snarfy say? If we can break Kirchoff's Law, for
       even .1 millisecond, what next?  Total  Anarchy  in  the  physics
       world ? Heavens forbid!
Newsgroups: sci.physics