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Resistance in a light bulb

  • Thread starter Xels
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  • #1
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Homework Statement


A "90-watt" light bulb uses an average power of 90W when connected to an rms voltage of 120V .

What is the resistance of the lightbulb?


Homework Equations



Pav=(V2rms/R)

The Attempt at a Solution



90W = 120V2/R
90W/120V2 = R
R = .00625[tex]\Omega[/tex]
 
Last edited:

Answers and Replies

  • #2
gneill
Mentor
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You have an algebra problem with your solving for R.
 
  • #3
19
0
Hrmm...

P = V2/R
PR = V2
R = V2/P
R = 160[tex]\Omega[/tex]

That works better huh? Thank you!
 

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