Re: Physics for Electricians

["John S. Denker" <jsd@MONMOUTH.COM>]

Tina Fanetti wrote:
> hmm I wonder why it came all messed up

There are probably 500 people wondering what "it"
refers to.

Suggestion:  When replying to a message, quote the
relevant parts and attach the reply thereto.  Otherwise
folks have no idea which of 100+ possible antecedents
"it" has.

(OTOH please do not quote _more_ than the necessary
relevant context;  that makes things less clear, not
more clear.)

> The things I understand only take half the semester...
> is what i meant.

Welcome to teaching.  Nobody ever understands anything
until they try to teach it.

> I think I have a plan...I asked the students what they wanted to know

That's a good thing to do.  Ask 'em early and often.
But you can't stop there.  They will know a few things
about what they want to know, but in general there are
innumerable things they need to know, but they don't
even know how to ask about.

==========================================

If you think of these kids as just the electricians
who pull Romex through half-built houses, you're on
the wrong track.  They don't need to know any physics
to do that.  But there are lots of other things that
IBEW electricians are called upon to deal with:
 -- Coax for TV cable.
 -- Coax for data, e.g. ethernet.
 -- Cat-5 twisted pair for phone and ethernet
 -- Optical fiber

NOTE: I'M NOT EXPECTING YOU TO KNOW ALL THIS STUFF,
BUT YOU CAN FIGURE IT OUT.  IF YOU CAN'T FIGURE IT
OUT IN THE AVAILABLE TIME, FORM TEAMS OF STUDENTS
AND ASSIGN A TOPIC TO EACH TEAM.  REQUIRE THEM TO
FIGURE IT OUT AND REPORT BACK IN ONE WEEK (FOR THE
EASY TOPICS) OR TWO OR THREE WEEKS (HARDER TOPICS).
THEN EVERYBODY (YOU INCLUDED) CAN LEARN IT TOGETHER.

They might want to know enough physics to understand
why the techniques you use for splicing 16-gauge lamp
cord are not appropriate for splicing coax.  And why
you don't want to crimp optical fiber around a sharp
corner.  And why Pupin put loading coils on long-haul
telephone circuits, and why such coils are death to
DSL.  And why running DSL for 30,000 feet is !!not!!
twice as hard as running it for 15,000 feet.  Hint:
what's a dB?  And why multiple ethernet jacks are not
wired in parallel like extension phones.

Conservation of energy as applied to transformers.
Energy efficiency.  Energy dissipation.

What's inside these new compact fluorescent
bulbs;  why are they so much more efficient than
incandescents?  And what about these new white LEDs;
are LEDs going to replace all other forms of lighting?

How the transformer on the pole behind your house
serves to regulate voltage (saturable core).

Health effects of exposure to radio waves and
microwaves.  Health effects of plain old electricity,
as a function of current, voltage, and frequency.

AC circuits.  Phase.  Power factor.  Voltmeters,
ammeters, and power meters.

The physics of arcs and sparks.  The tricks they
use to extinguish the arc in a high-power circuit
breaker.  (Very clever, very interesting IMHO.)

Grounding and shielding.  How to keep high-power
radio transmitters and/or powerlines from trashing
TV and/or data signals.

============

In addition to asking the students (good first step)
and asking phys-l (good second step), also look in
the phone book and find the IBEW local for your area.
Call up the Master Poo-Bah and ask him what he knows,
what he wished somebody had taught him, and what he
wishes somebody would teach the newcomers.