Sean Breheny wrote:
> 
> Here's another little mystery regarding Neon lamps:
> 
> I have sometimes taken a Neon-bulb based AC voltage tester and only plugged
> the one lead into the hot side and left the other side floating in the air.
> What I observed was a dim glow only near ONE of the two electrodes. My
> guess is that what is happening is that the glow is only emitted where
> electrons are hitting an electrode inside the lamp, and that this actually
> indicates that a small current is flowing in only one direction through the
> lamp. Possibly the lead floating in the air has a rectifying effect due to
> there being more cations than anions (or vice versa) in the air?
> 
> Any ideas?

I guess that the human body working as a "mass antenna" offers plenty of
resistance to current flow, so when the outlet "hot" wire has a positive
level, your body can not supply enough electrons to the lamp to glow. 
By the other side, when the outlet supply the negative level, there are
plenty of electrons to flow and spread into the human body (in a funnel
situation), and that generates the dim glow.

I also believe that the itching shock you feel when touching a
non-grounded machine frame, it most generated by the negative side of
the senoid than the positive.

You can confirm this situation touching a 150 VDC with the lamp (and
resistor) positive to lamp, negative to ground, and then reverse the
polarity. I guess the lamp will only glow when the 150Vdc negative is
connected to the lamp.

This same effect you can feel (energy transfer) when touching an ice
cube or a warm/hot material.  Suppose the ice cube is at -10¡C and your
finger is at +33¡C, there is a delta thermal of 42¡C, so, warm a piece
of metal to 33+42 = 75¡C and fast touch the ice cube then the metal.  I
am able to feel easily the delta temperature from the metal block. What
can you feel easily in a room with constant ambient noise?  a peak of
higher noise, or a peak or silence?... a peak of lightness or a peak of
darkness? 

Ok, ok, I can feel easily a negative peak in the bank account, rather
than a positive one... hmmm... probably because I never had the
opportunity... :)

Wagner.


> 
> What does a Neon bulb normally do when connected to DC (I didn't think to
> try it until just now, but I don't have one handy)? Does only one electrode
> glow?
> 
> Sean