Filament radiation in light bulb

In summary, a 3-inch diameter light bulb with a filament surface area of 2.5 X 10-3 ft2 and operating at 2240 F has an emissivity of 1.0 and radiates through a vacuum to the glass wall. Only 10 percent of the emitted energy is absorbed by the glass, which subsequently loses heat to the surroundings at a temperature of 80 F through both radiation and natural convection. The heat transfer coefficient for natural convection is 1.17 BTU / hr ft2 F. Using equations for convection and radiation, the surface temperature of the bulb can be calculated.
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Homework Statement


A light bulb has an internal filament with a total surface area of 2.5 X 10-3 ft2 that operates at a temperature of 2240 F. The filament has an emissivity of 1.0 and radiates through a vacuum to the glass wall of the bulb. Only 10 percent of the total energy emitted as radiation from the filament is absorbed by the surrounding glass bulb. Heat that is absorbed by the glass bulb is subsequently lost from the outer surface of the glass bulb (ε = 1.0) by both radiation and natural convection to the surroundings (surrounding temperature = 80 F). The heat transfer coefficient for natural convection under these conditions is 1.17 BTU / hr ft2 F.

What is the surface temperature of the bulb assuming the bulb can be modeled as a sphere 3 inches in diameter?



Homework Equations





The Attempt at a Solution


I calculated the convection term and radiation from the glass to the surroundings, and set it equal to 0.1*energy from filament to glass. I am not sure if my expressions are correct for all these various forms of heat transfer.
 

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1. What is filament radiation in a light bulb?

Filament radiation in a light bulb is a process where an electric current passes through a thin wire, known as the filament, causing it to heat up and produce light. This is the basic mechanism behind incandescent light bulbs.

2. How does the filament produce light?

The filament in a light bulb is made of a material with a high melting point, such as tungsten. When an electric current passes through the filament, it heats up to a very high temperature, causing it to emit electromagnetic radiation in the form of visible light.

3. What is the color of filament radiation?

The color of the filament radiation depends on the temperature of the filament. As the temperature increases, the color shifts from red to orange, yellow, and eventually white. This is known as the black-body radiation curve, and it is used to determine the color temperature of a light source.

4. How efficient is filament radiation in light bulbs?

Filament radiation in light bulbs is not very efficient, as a large portion of the energy used is converted into heat instead of light. Only about 10% of the energy is actually converted into visible light, making incandescent bulbs one of the least efficient lighting options.

5. Why are incandescent bulbs being phased out in favor of other lighting options?

Due to their low efficiency, incandescent bulbs are being phased out in many countries and replaced with more energy-efficient options such as LED and CFL bulbs. This is to reduce energy consumption and carbon emissions, as well as save consumers money on their electricity bills.

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