The tungsten filament inside a light bulb is heated to a temperature of 1250 K.It has a surface area 2 cm².What is the net power radiated by the light bulb at room temperature (25 $\circ$ C)? (emissivity of tungsten is 0.7)

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Quizplus · Accepted Answer

The net power radiated can be calculated using the Stefan-Boltzmann law: $ P = e\sigma A(T^4 - T_0^4) $, where $ e $ is the emissivity, $ \sigma $ is the Stefan-Boltzmann constant ($5.67 \times 10^{-8} \, \text{W/m}^2\text{K}^4$), $ A $ is the area in m², $ T $ is the filament temperature, and $ T_0 $ is the room temperature. Converting the area to m² (0.0002 m²) and room temperature to Kelvin (298 K), the calculation gives approximately 19 W.

The Tungsten Filament Inside a Light Bulb Is Heated to a Temperature