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What is the current in each bulb?

  1. Aug 15, 2011 #1
    Two 40-watt bulbs are connected in parallel to a 120-volt circuit. What is the current in each bulb?
    Choose one answer.
    a. 1/4 A
    b. 1/3 A
    c. 1/2 A
    d. 2 A
    e. 3 A

    I used V = IR and P = V^2/R

    My attempt
    40 W = 120V^2 / R giving R = 360
    1/R + 1/R = 1/Req => 1/360 + 1/360 = 1/Req => Req = 180ohms
    V=IR => 120 = 180I => I = 2/3
    which is not an answer
     
    Last edited: Aug 15, 2011
  2. jcsd
  3. Aug 15, 2011 #2
    Re: Circuits

    You found the total current (correctly), but the question asks for the current through each bulb.
     
  4. Aug 15, 2011 #3
    Re: Circuits

    You don't need to calculate resistance here, assume the total current is [tex]I[/tex] , then [tex]I= \frac{80w}{120V}=\frac{2}{3} Amp[/tex], the current in each bulb should be [tex]\frac{1}{3} Amp[/tex]
     
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