Thermodynamics question: temperature between layers

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Adam Rabe
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Homework Statement



Multiple-choice physics problem text about a penguin's feather insulation, with answer options (A) -12, (B) -7.7, (C) -2.0, (D) 3.5, (E) 6.9.


Homework Equations


h = k/d
1/h (total) = 1/h + 1/h + 1/h... + 1/h (surf)
Q/t = h A T

The Attempt at a Solution


For the thermodynamic one i got up to calculating the total heat transfer coeffecient but i don't know where to go from there as its asking for the outside temperature of the feathers, whilst giving an air temperature (-15 degrees).

Help would be greatly appreciated ~ Adam
 
Could you sketch the thermal "circuit" showing the temperature points and thermal resistance between each? Think ratios or "potential divider" if familiar with electronics.
 
CWatters said:
Could you sketch the thermal "circuit" showing the temperature points and thermal resistance between each? Think ratios or "potential divider" if familiar with electronics.
Hello i tried sketching the circuit but i just can't seem to get it. Is there some sort of 3rd layer between the feathers and air? If so how would i go about finding the temperature of it? Also I am not familiar with potential dividers
 
Look up "surface heat transfer coefficient". The "third layer" as you called it is the surface of the feathers.
 
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