Volume 13 Number 38
Produced: Tue May 31 22:36:21 1994
Subjects Discussed In This Issue:
Circuits
[Gedalyah Berger]
Electricity
[Mechy Frankel]
Personal phone calls
[Charles R. Azer]
Yosef and bitachon
["Yitzchok Adlerstein"]
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From: Gedalyah Berger <gberger@...>
Date: Sun, 22 May 1994 21:23:00 -0400
Subject: Circuits
This seems to be turning into a discussion about physics and not
halachah, but as long as our moderator allows it I'll respond. As a
reminder, this issue arose because of the Chazon Ish's contention [in the
context of the halachic status of electric circuits regarding the
prohibition on Shabbos of "building"] (as quoted by someone on the list)
that an electric circuit is different from water flowing through a pipe
because the electrons are an integral part of the wire, while the water
is not an integral part of the pipe.
Eli Turkel wrote:
>Gedalia (sic) Berger writes:
>> The water and the pipe are indeed separate entities, while the
>> electrons which comprise the current are part of the crystal structure of
>> the metal wire; if (even just the conduction band) electrons were not
>> there, the material would be completely different (if it would remain
>> solid at all). A pipe is a pipe, water or no water.
> Electricity moves at the speed of the electromagnetic waves that
> propogate down the conductor not at the speed of the elctrons within
> the metal wire. In fact the electrons individually move only a very
> small distance. Hence the existence of an electrical circuit does
> not materially change the physical properties of the wire.
A few comments:
1) "Electricity" doesn't "move"; the word "electricity" doesn't refer to
any object or specific physical property, but to a branch of science.
This is anologous to speaking of the "motion" of chemistry.
2) A current does not consist of a propagating electromagnetic wave; when
a dc circuit is closed, it is indeed true that the change in voltage
moves down the wire at a speed of c, but *very* quickly a steady state is
reached in which there is no longer propagation of an electromagnetic
disturbance. The potential (=voltage) at any given point on the wire then
has a value constant in time. The only things "flowing" in an electric
circuit (and such flow is the only basis for the comparison with pipes to
begin with) are electrons.
3) It is not true that the electrons move "only a small distance." They
actually travel around and around the circuit. It is true that they
travel at a "small" velocity, at least relative to the speed of light.
Their average "drift velocity" is of the order of 1 cm/sec, which means
that in a circuit one centimeter in circumference an average electron
would make one revolution per second.
4) I never claimed that the "existence of an electrical
circuit...materially changes the physical properties of the wire"
(although that is arguably true as well, depending on what you mean by
"physical property"); I only said that the electrons are part and parcel
of the wire itself (current or no current), while water is not part of a
pipe.
Kol tuv,
Gedalyah Berger
Yeshiva College ("Torah U'Maddah") / RIETS
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From: Mechy Frankel <frankel@...>
Date: Fri, 20 May 1994 18:18:05 -0400
Subject: Electricity
While I suspect this isn't the best forum for such a discussion, since
it was raised I should like to both offer a correction and melamaid
zechus to Eli Turkel's characterization (Vol 13 #18) of electricity as
moving at the speed of the electromagnetic waves that propagate down the
wire, not the speed of the electrons within the metal wire" and that
"the electrons individually only move a very small distance". I'd like
to melamaid zechus since I so often find myself in agreement (my own
test of an intelligent fellow) with whatever Eli may be writing about
that I should certainly feel unhappy rejecting something without
applying at least a few microseconds of deep thought.
1. First for the speed of light. (This is my melamaid zechus
interpretation). There is one sense in which "electricity" does move
with the speed of light. If, say, a circuit was closed at some point by
closing a switch, the effects of that circuit completion will be felt
along the circuit wire at different points, with a delay equal to the
time light can propagate the information that the circuit is now closed.
to that location i.e. the applied e-field (which makes the electrons
move) propagates with velocity of light and that's when the conduction
electrons at that location start moving. This is, I suppose, what Eli
was referring to. I believe that most people however associate the speed
of "electricity" with the speed of the electric "current", which
involves the actual motion of the charge carriers (bare electrons in
simple systems) which, as Eli and everybody else knows, can't move with
the velocity of light since electrons have non-zero mass. I think the
awkwardness of Eli's usage versus the conventional one is apparent if we
consider applying both to desciption of a case where the entire current
consists of a single electron travelling through space in response to a
field.
2. Alas, I cannot salvage any point of agreement on his second point
that the electrons actually don't move very much. The electrons in a
conductor do, of course, move macro distances in response to the
externally applied electric force in the wire (driven e.g. by the
potential difference supplied by a battery). This occurs because the
binding force on the outer shell/conduction band electrons is less than
the qE (battery) applied electric force (alternatively, for some
energies, the metal atoms simply have no bound states), which is thus
able to completely remove the conduction electrons from their local
crystal sites and shove them along down the wire. Of course, physicists
can and do snazz this picture up considerably with descriptions of the
non-localized and collective nature of the many-particle system of
electrons in metals and whatnot. (see Ziman, or whatever they're using
in schools to teach condensed matter theory these days). But the bottom
line is, as Galileo is rumored to have muttered (in perfect English),
"yet, it moves".
Mechy Frankel H: (301) 593-3949
<frankel@...> W: (703) 325-1277
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From: Charles R. Azer <azer@...>
Date: Mon, 23 May 1994 12:10:08 -0400 (EDT)
Subject: Personal phone calls
> For example, I once worked in a company where official
> policy was that one could not make personal phone calls. However,
> pretty much everyone including management did. I asked Rav Heineman if
> I am allowed to make personal calls (of course withing reason - one or
> two locals calls home aday). He said that its OK to make the calls,
> since that is the accepted behaviour in the office.
Unbelievable! So what the rabbi is saying is that a proponderance of
wrongs make a right. If enough people do things against the law, then
it's O.K. for you to do so, as well.
I remember hearing that one is supposed to follow the law of the
land--provided it doesn't contradict halacha. So bringing up another
topic I've seen mentioned recently--speeding--I guess the rabbi would
probably also agree that it's O.K. to speed since it's the general
accepted practice.
None of us is perfect. We all do things we shouldn't do. But we
shouldn't justify doing these things based on how others are behaving.
If Judaism is a religion of absolute truth, then in assessing what we
should be doing, we should ignore what others are doing. Otherwise...
you might as well give it up entirely--after all, it's only a small
percentage of Jews that keep the majority of the mitzvot, or even just
Shabbat or kashrut.
Chuck
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From: "Yitzchok Adlerstein" <ny000594@...>
Date: Sun, 22 May 94 22:37:45 -0800
Subject: Yosef and bitachon
Rightfully so, recent correspondance about Yosef and his extra two
years in captivity reflects much of the common confusion about the
mitzvah of bitachon - of trust in Hashem and His Providence.
Several participants have questioned the assumed error in Yosef's
soliciting the help of his cellmate, and Hashem's subsequent
displeasure. I hope that the following, based on the works of Rav
Eliyahu Dessler and the Bais HaLevi, will be helpful.
The Torah eschews quietism. It doesn't allow us to kick back and
let HKB"H take care of things for us. Somehow, in the world after
the sin of Adam, it is in Man's interest to live in the world of
teva, of natural law and predictable consequence.
On the other hand, "Ein Od Milvado" - "there is nothing besides
Him" is a fundamental and cherished principle. Nothing exists
outside of Him. (Not pantheism, but panentheism, as Gershom Scholem
called it.) Nothing exists independent of His Will - not angels,
not natural law, nothing. To have it any other way would diminish
the absolute Oneness of Hashem.
The tension created by these principles is a paradox we live with
each day. We are bidden to live in a real world that behaves as if
it were self-propelled, but firmly believe that only the Great
Pilot keeps the ship aloft. We live guided by certain natural
"realities," while understanding that we do so only because Hashem
demands it. It is no harder for Him to get things done here
without our assistance than with it; He has merely chosen to
demand that we pay the price of Hishtadlus, of human endeavor and
effort. (Every now and then, He in fact accomplishes things
without taking heed of the usual laws, and a miracle ensues. But
as Ramban says, the upshot of all miracles as that all is
miraculous. The usual flowing of the Red Sea is no more or less
miraculous than its splitting. They are both consequences of
Hashem's Will.) Our job is not to be fooled by it. The farmer,
accustomed to pitting his brains and brawn against the elements,
can easily attribute his succesful harvest to his own energies and
talents. Instead, the Torah tells him - multiple times - to
recognize that it was only Hashem's Will that married the farmer's
efforts with success.
A bottom line is that there is an antagonistic relationship between
hishtadlus (human effort) and bitachon. The more a person is aware
of Hashem as the Animator of all, the more bitachon he has - the
less hishtadlus he is required to produce. The effort put in by a
person at one level of bitachon accomplishment would be too much
for another, and not enough for yet a third person.
Yosef is not faulted for asking the help of his cellmate. We are
supposed to be active. But Yosef was on such an advanced level of
bitachon, that the amount of effort he put in was perhaps beneath
him. He should have enlisted the aid that he did. But knowing how
Hashem stood behind him, he should not have felt a heightened sense
of expectation of release that he did. Seeing the "light at the
end of the tunnel" should not have had an impact on him. After
all, "Hayad Hashem tiktzor?" Does Hashem's Hand lack? If Hashem
wanted to deliver Yosef on a particular day, did He lack ways of
accomplishing his release? Why should the presence of a potential
ally (his release cellmate) make Yosef perk up on this day, more
than on any other? Yosef should have seized the moment to do his
thing - and then waited with the same hope for Divine intervention
he felt ANY OTHER DAY OF HIS CAPTIVITY!
Instead, Yosef placed a bit too much emphasis on the quality of his
plan and its efficacy, rather than on the certainty of Hashem's
ability to produce, with or without a plan discernible to humans.
After two years he learned his lesson. Thus, when he is brought
before Paroh, and once more given an opportunity to manufacture his
own release, Yosef acts very differently. Yosef's ability to
interpret dreams has been hyped to a worried and sleepless Paroh.
He's heard that Yosef can be effective. "Biladai," says Yosef.
"It's not me. I can do nothing. It all comes from Hashem."
Having reminded himself of this and having stated it forcefully, he can
then pursue the lifeline that Hashem indeed extended to him, and
follow through with his hishtadlus, confident that it will not
diminish his bitachon.
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End of Volume 13 Issue 38
