1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Transfer of heat question

  1. Apr 20, 2010 #1
    1. The problem statement, all variables and given/known data

    The amount of heat per second conducted from the blood capillaries beneath the skin to the
    surface is 240 J. The energy is transferred a distance of 2.0×10−3mthrough a body whose surface area is 1.6 m2. Assuming that the thermal conductivity is that of body fat 0.2 J /(s ⋅m⋅o C) , determine the temperature difference between the capillaries and the surface of the skin.

    So k = .2
    A = 1.6 m^2
    L = 2.0 x 10^-3m

    I'm not sure what the 240 J goes as? Is that Q?


    2. Relevant equations

    This is basically where I'm stuck... I'm not sure what equation to use.

    I was thinking possibly Q = k * A * change in T * time all divided by L .... but there's no mention of time?


    3. The attempt at a solution
     
  2. jcsd
  3. Apr 21, 2010 #2
    You wrote down the right equation. Notice that give you a rate of heat transfer so you can divide time over to the left side of the equation.

    Then it's just a substitution of information problem.
     
  4. Apr 21, 2010 #3
    So...

    Q/t = k * A * change in T / L

    240 = .2 * 1.6 * change in T / 2 X 10^-3

    So the answer would be 1.5 degrees?

    I think that's right... thanks
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook