Subject: Modeling the resistance of a tungsten filament , incadescent light bulb.

I know that the resistance of the tungsten filament depends upon the 
resistivity of the tungsten metal, the cross section of the filament 
wire and the temperature of the metal filament.  Is there formulation 
or a set of equations that relates the filament resistance and 
filament temperature to the DC or RMS current passing through the 
filament at a specified time?  I assume that steady state thermal 
conditions exist when the filament temperature and filament 
resistance are calculated.  

Re: Modeling the resistance of a tungsten filament , incadescent light bulb.