27 Nov
2014
27 Nov
'14
11:39 a.m.
Hi Chuck,
The lack of heating in your antimagnetic stainless or copper cookware isn't
due to a lack of ferromagnetic content - it's a different situation
entirely. The issue stems from the electrical properties of the bulk
material - in essence, those pots are +too good+ of a conductor at the
frequencies in use. The currents flow in a deep, thick layer and encounter
trivial resistance. It's this lack of resistance that's responsible for the
lack of heat production .
I'm sure you've seen the well-known 'magnet down the copper pipe'
demonstration, which shows clearly that eddy currents develop just fine in
copper - which certainly isn't in the ferromagnetic series. As for glass or
ceramic, they're electrical insulators, so there's little to zero current
flow at all, and again, no heat production.
On Thu, Nov 27, 2014 at 1:00 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 11/27/2014 06:17 AM, Mouse wrote:
(But it has its own downsides, like not working with glass pans - I
have a glass skillet....)
It's more serious than that. The cooking utensil has to be
ferromagnetic. So, my substantial investment in 18/10 stainless steel
cookware is out; however, cheap 18/0 stainless works fine. My Le Creuset
porcelain-over-cast iron are fine as are my All-Clad stainless.
I have a considerable inventory of older borosilicate Pyrex (not the cheap
soda-lime that passes for Pyrex nowadays) as well as pieces of Corning
glasswre that are more than 40 years old. Those get relegated to ovenware
and storage. Fortunately, better makers of cookware are now starting to
laminate a steel insert into pot bottoms. Given the low thermal
conductivity of glass, I've wondered if cooktop use can be justified But
induction's come a long way since Princess Margaret started using it.
Interesting! What _does_ account for most of the draw? Are you in an
area where electric is common as the energy
source for routine heat?
Thinking about my own experience, I'm fairly confident the ranking goes
heating (if electrical), computers, cooking, and then everything else
is down in the noise - and that's for me personally; most people don't
have nearly the computer load I do.
Other than living space heating, I understand that a water heater accounts
for a substantial part of an all-electric home's energy consumption.
Lighting also used to be high on the list, but since CFL adoption has
picked up, I don't think that it accounts for the load that it once did.
Eventually, LEDs can be expected to supplant CFLs.
I've wondered about that. SMPSUs draw no current most of the cycle,
drawing heavily on the peaks, without the
smoothing effect of the mains
transformer present in (most) non-switching supplies. This is almost
nothing like most historical load, which is mostly either resistive or
inductive. I'm curious whether it has a significant effect on the
grid; do you happen to know?
"Dirty" harmonic-laden current from SMPSUs is a problem. But that problem
also arises from the lowly CFL. Right now, the problem is being mostly
ignored. I read an interesting paper that suggests that HVDC for large
server farms may be the best answer in that case.
--Chuck