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Homework Help: Conductivity homework problem

  1. Apr 2, 2010 #1
    1. The problem statement, all variables and given/known data

    There are 2 nichrome wires P and Q are connected in series to battery of emf , V .
    Both P and Q are of same length bu the diameter of wire P is bigger than that of wire Q . When wire P and Q glow steadily , which one would glow brighter ?

    2. Relevant equations



    3. The attempt at a solution

    What determines the brightness of the nichome wire ? Is it the temperature(as in when its hotter it glows more) ? Then how is different when the nichrome wires are connected in parallel ?
     
  2. jcsd
  3. Apr 2, 2010 #2
    Re: conductivity

    Yes, the brightness will be determined by the temperature. The temperature will be determined by the power dissipated in the wire when a steady state has been reached.
    You need an equation that relates the power in the wire to its resistance, and an equation that relates the resistance of the wire to its cross section.
     
  4. Apr 2, 2010 #3
    Re: conductivity

    thanks !
     
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