jeff_wisnia wrote:
Oren wrote:
On Sat, 21 Nov 2009 13:33:28 -0800, David Nebenzahl
wrote:


On 11/21/2009 12:19 PM Higgs Boson spake thus:


On Nov 21, 12:06 pm, David Nebenzahl wrote:

On 11/21/2009 11:51 AM Higgs Boson spake thus:


Am about to replace hideous doorbell. AFAIK, I just have to unscrew
tthe old one and attach the new one to the wires.
BUT - how do I know which "breaker" as they used to call them,

Still do.


controls the doorbell? I looked in my switch box, where I have
everything labeled, but did not see "doorbell". It rings in the
kitchen. Anybody hazard a guess where it might be connected?

Could be on any breaker; no official rule for where to put a doorbell.

Probably several ways to skin this cat. One would be to put a
voltmeter
on the transformer (that's the thing that supplies low voltage
power--typically 16-24 volts--to the actual doorbell) and flip
breakers
until it goes to zero volts (assuming the transformer works). Probably
the safest way; that secondary (low-voltage) side of the transformer
isn't going to hurt you if you get shocked by it.

Friend told me that if I just touch one wire at a time, I won't get
shocked.
T/F? Makes sense ; circuit not completed; but hard to isolate wires
in small space.

Welllll, that's true in *theory*. But probably lots of folks have
been hurt (or even killed) when theoretically impossible.

Just to be clear, there are two issues he

1. Whether or not you can get shocked by just touching one wire of a
circuit.
2. Low voltage vs. high voltage.

First issue: yes, in theory if you touch only the hot wire of a
circuit, you won't get shocked. (Works for birds sitting on powerline
wires, for instance). Problem is there are other sneaky way of the
circuit completing itself, like through damp ground, your shoes and
your feet. So the best policy is to never touch *any* wires
(energized ones, that is).

Second issue: As I said, doorbells operate on low voltage (somewhere
in the range of 12 to 24 volts AC). Getting shocked by such low
voltages is a lot safer than high voltage (like the 120 volts in your
household wiring). While it is theoretically possible to get
electrocuted from even a low-voltage shock, it's unlikely. So it's
safer messing around with low-voltage wiring that may be live than
high-voltage wiring. Still not recommended (see best policy above).


I cannot recall the exact details, but I'm sure it had to do with
moisture. Working on a 12V truck battery, I got "bit". Not sure what
was touched by the tools or the wetness and leaning against the truck
fender.

I was "shocked" it could happen. Hasn't happened since.

Didja ever try simultaneously touching both contacts of a little 9 volt
"transistor radio" battery with your tongue?

Jeff


You should try sticking a 98 volt battery to your forehead.
There is a little sting to it but the most interesting part
is the disruption to your vision. It's as though a movie
camera shutter was being flicked open and closed at a rapid
rate but slow enough to be perceived, very odd sensation. I
didn't try it with the 525 volt batteries that were used by
my Graflex Stroboflash IV with which I could strike quite
an impressive electric arc. I miss that thing, I could melt
retinas with it and it was fun at parties.

TDD