Although caution must be used in applying = 0 (1+T) and R = R 0 (1+ T) for temperature changes greater than 100C,

Although caution must be used in applying ρ = ρ₀(1+αΔT) and R = R₀(1+ αΔT) for temperature changes greater than 100°C, for tungsten the equations work reasonably well for very large temperature changes. What, then, is the resistance of the tungsten filament in the previous example if its temperature is increased from room temperature (20°C) to a typical operating temperature of 2850°C?

Strategy

This is a straightforward application of R = R₀(1+ αΔT), since the original resistance of the filament was given to be R₀ = 0.350 Ω, and the temperature change is ΔT = 2830°C.