Incandescent Light Bulbs 1 Incandescent Light Bulbs

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Transcript of Incandescent Light Bulbs 1 Incandescent Light Bulbs

How Things WorkQuestion:
An incandescent light bulb contains some gas with the filament. How would removing the gas affect the bulb’s energy efficiency?
Make it more efficient
Make it less efficient
Light bulbs glow yellow-white
You can feel heat radiating from them
They burn out
They come in many specialized types
Incandescent Light Bulbs *
All materials
emit electro-
Incandescent Light Bulbs *
Black Body Spectrum
The spectrum and intensity of electromagnetic waves from a black body depend only on its temperature
Demonstration: Incandescent Light Bulb and Variac
Incandescent Light Bulbs *
Incandescent Light Bulbs *
Filament heating
Requires thinner filament at higher voltages
Demonstration: Incandescent Bulb and Variac, Including OVERVOLTAGE
Demonstration: Different Wattage Incandescent Bulbs
Demonstration: Open Incandescent Bulb
Filament sublimation
Non-reactive gas limits sublimation
Gas leads to convective heat loss
Demonstration: Operate and Burn Up Open Incandescent Bulb
Incandescent Light Bulbs *
Question:
An incandescent light bulb contains some gas with the filament. How would removing the gas affect the bulb’s energy efficiency?
Make it more efficient
Make it less efficient
Solids expand when heated
Some materials expand more
than others when heated
glass and wires must expand equally
Incandescent Light Bulbs *
Bulb has small, high temperature envelope
Produces a filament recycling process
Demonstration: Compare Bulb-shaped Halogen with Conventional Bulb
Demonstration: 12V Halogen and Battery
Demonstration: Halogen Rod Lamp (500W)
Incandescent Light Bulbs *
Rough service bulbs
Demonstration: Rough Service Bulbs (Clear)
Demonstration: Extended Life Bulbs
Most of their thermal radiation is not visible
They fail when the filament sublimes away
The glass envelope keeps oxygen out
The inert gas fill lengthens the filament life