Hello
I am retired and I guess by now everyone on here knows I have way too much time on my hands,
I have been known to change the air in my tires.
That said I do have a way to prove the fact not theory that a incandescent light bulbs resistance
goes up when you apply voltage to it.
If you check the resistance of a 100 watt 120 volt light bulbs it reads around 12 ohms. This is around
the resistance of a 4500 watt water heater Element.
Below is a link to a wire identifier I built it works with a resistance bridge which applies a 36 volts to the
conductor under test. On the #2 setting the resistance has to fall within a range between 10 and 20 ohms.
Which I also use to test water Heater Elements. If the Element is good the tester light goes out and stays out
which means the resistance is within the 10 to 20 ohm range not shorted and not open, either one of those and
the tester light will remain on.
On the #2 setting with the wire Identifier when you first put the leads on a 100 watt light bulb the tester light will extinguish for about 1/2 of 1 second.
In other words once the 36 volts from the tester heats the bulbs filament the resistance goes out of 10 to 20 ohms
range which takes about a 1/2 of a second and the testers light bulb comes back on.
The water heater tester will not work because the applied 3 volt voltage is to low to heat the light bulb filament so the
Tester light stays off of course this is just more proof the heat is what does it.
You can actually feel the bulb get warm with the 36 volts applied to it with the wire Identifier.
Now I expect everyone to build both of these testers just to see if this is true. :roll:
Oh I all most forgot here are the links.
Click here for wire Identifier
Click here for Water Heater Tester
Thanks:Ronald