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March 28, 2017

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A 40 W (120V) light bulb has a tungsten filament of thickness 0.035 mm. The filament's operating temperature is 1500 degrees C.

PART A
How long is the filament?

PART B
What is the resistance of the filament at 20 degrees C?

  • Physics - ,

    look up the resisitive of tungsten at 1500C. you know area, compute length from known resistance (Power=V^2/R)

  • Physics - ,

    Power= V^2/R
    40=120^2/R
    R=360

    R=pL/A
    RA/p=L
    (360)(pir^2)/(5.0x10^-7)=L
    L= 2.77
    (5.0x10^7) is the reisisttivity of tugsten at 1500 degrees

  • Physics - ,

    sf

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