w_tom wrote:
Light bulbs work at may voltages. For example, a 120 volt
incandescant bulb will work at 60 volts AND last for maybe 100 years
continuous. As voltage drops, bulb life expectancy increases
exponentially (about a factor of 12). As voltage drops, bulb
intensity also decreases exponentially. Sure, the 12 volt bulb will
work at 6 volts. But its light output will be massively diminished
and its efficiency is decreases (less light per amp of electricity).

So yes, a 12 volt lamp will work on 6 volts (if power supply can
provide sufficient current). Just not work very well.

NO, it will not. There will be insufficient heat in the element to provide
any light or even a glow with a 12V bulb at 6V DC. A 12VDC bulb will begin
to dim substantially at 9 VDC and may not even be visible in the light of a
room.

Do not profess knowledge you do not have.


On Feb 14, 10:21 am, "HK" wrote:
I'm trying to help my daughter with a school project and while I
know my way around house wiring, I'm a relative newbie when it comes
to low voltage.

Let's say I have a 6 volt DC power supply (4 "C" batteries). If I
want to drive a small motor and some lights, I just find 6 volt
motors and lights and wire them in parallel or series.

Why is it that I can't light up a 12v light with a 6 volt power
supply? I always test my batteries using a multi-meter and as the
battery ages, the voltage drops. With low voltage, the device
(flashlight, etc.) still works but the light is weak. So, wouldn't
a 12v light just be weak if I use a 6v power supply?