Tony Hwang wrote:
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?

Is there some kind of voltage threshold at which a device won't work?

Like I said, basic question.

Hi,
It depends on the lamp's rating. If you lower the voltage to half you
have to double the current to get same Wattage. Can the battery do that
with the lamp you have? Automotive type bulb draws quite bit of curent.
Hi,
And what differene does it make? High voltage or low voltage circuit.
Basically it is all govenred by simple Ohm's law.