The Tungsten Filament of a Light Bulb Has an Operating $\sigma$

question 9

Multiple Choice

The tungsten filament of a light bulb has an operating temperature of about 2100 K. If the emitting area of the filament is 0.80 cm², and its emissivity is 0.68, what is the power output of the light bulb? ( $\sigma$ = 5.67 *10^-8 W/m² ·K⁴)

• A) 100 W
• B) 75 W
• C) 60 W
• D) 40 W

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