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Homework Help: Wires in an circuit, different materials, heat

  1. Jan 2, 2018 #1
    1. The problem statement, all variables and given/known data
    In an electric circuit, consisting of copper wires with cross section area of Sc=5mm2 and a temperature of t=25C, a lead fuse is added melting when the copper wire temperature increases by Δt=25C. Find the cross section area of the lead fuse wire Sl=x.
    specific heat: cc=400J/kg*C cl=140J/kg*C.
    Lead melting point tl=327C, latent heat λ=25000J/kg.
    Specific electrical resistances of the materials: ρc=0,017*10-6Ωm, ρl=0,21*10-6Ωm.
    material density: ρc1=8,9*103kg/m3, ρl1=11,34*103kg/m3.

    2. Relevant equations

    Thank you for any ideas on how to solve this, if there is something confusing please ask, this equation is translated from a different language so there may be inaccuracies and such.
  2. jcsd
  3. Jan 2, 2018 #2


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    Don't erase the part 3. Attempt at solution. We can't help if you don't post that...
  4. Jan 2, 2018 #3
    I was asking for ideas, directions to try going towards, I'm not asking people to solve it. Anyway, I was thinking about Q1=Q2 Q1=ccm1Δt Q2=cl(tl-t). But I don't know the masses nor anything derivative from it since I need to find the cross section area.
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