A 60 W lamp has a filament at 3500°C in steady state. The glass bulb has radius 3 cm and wall thickness 0.5 mm. Assume no convection, take the inner wall at the filament temperature and the outer wall

Question

A 60 W lamp has a filament at 3500°C in steady state. The glass bulb has radius 3 cm and wall thickness 0.5 mm. Assume no convection, take the inner wall at the filament temperature and the outer wall at the air temperature of 27°C. Find the thermal conductivity of the glass, in units of 1 0 − 4 W m⁻¹ K⁻¹.

TestHub · Accepted Answer

A = 4 π 0.03 2 = 0.0113 m². k = A Δ T P d ​ = 0.0113 × 3473 60 × 0.5 × 1 0 − 3 ​ = 7.638 × 1 0 − 4 , so 7.64 × 1 0 − 4 .

Physics - Heat & Thermo Question with Solution | TestHub

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