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Homework Help: How to culculate rms current using Watts in a Household Curcuit

  1. Mar 25, 2013 #1
    1. The problem statement, all variables and given/known data

    Three lamps are connected in a household curcuit. Lamps 1 and 2 have 150W bulbs and lamp 3 has a 100W bulb. What is the Current (I) and Resistance (R) of each bulb?

    2. Relevant equations

    V=IR P = W/t = (V*q)t = V*I

    I= q/t V= W/q

    3. The attempt at a solution

    Lamp 1
    V=150W*1.6*10^-19 C?

    i'm not sure how to do this exactly. my teacher didn't explain very thoroughly. No time variable is given, no voltage, or current. I don't know how I can use Ohm's law.
  2. jcsd
  3. Mar 25, 2013 #2
    Can you assume standard household voltage ( like in India it is 220V rms)?
  4. Mar 27, 2013 #3

    I can assume a voltage, for the US household curcuot it's 120 V, and I can plug that into the P=VI to get my answer.Thanks!!
  5. Mar 28, 2013 #4


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    Science Advisor
    Homework Helper
    Gold Member

    Just for info - It can't be done any other way. You have to know the voltage.
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