A tungsten filament in a 60 W light bulb has a diameter of 0.04 mm and an electrical resistivity of 90 micro ohm cm. The filament loses heat to the environment, which is at 20 C, by thermal radiation. The emissivity of the filament is 0.32 and the voltage across it is 115 V. Find the length of the filament and the filament surface temperature. (Electrical resistance equals electrical resistivity times filament length divided by filament cross-sectional area.)
A tungsten filament in a 60 W light bulb has a diameter of 0.04 mm and an electrical resistivity of 90 micro ohm cm. The filament loses heat to the environment, which is at 20 C, by thermal radiation. The emissivity of the filament is 0.32 and the voltage across it is 115 V. Find the length of the filament and the filament surface temperature. (Electrical resistance equals electrical resistivity times filament length divided by filament cross-sectional area.)