# Homework Help: Problem with Conductivity

1. Apr 17, 2007

### cyberdx16

1. The problem statement, all variables and given/known data

A cylinder with a piston is filled with ideal gas. The gas temperature is held at 450 K. The cylinder is heated by an oven through a square metal rod connected between the oven and the cylinder. The rod has sides d = 1 cm and length L = 2.3 m.

(a) If the oven is held at 750 K, and the heat current conducted through the metal rod is 27 W, find the thermal conductivity of the metal in the rod.

k = W/m K
9 NO

HELP: H = k*A*(T2-T1) / L

HELP: H is the heat current; k is thermal conductivity; T2 and T1 are temperatures at two ends; A and L are cross-sectional area and length of the rod.

2. Relevant equations

H = k*A*(T2-T1) / L

3. The attempt at a solution

27=k(.023m^2)(300k)/2.3m

k=9

I'm pretty sure im right here... the following quesion asks,

For a larger cylinder at 450 K, a heat current of 57 W is needed. If we use the same metal rod to conduct heat, find the oven temperature in Kelvin that will maintain the necessary heat current.

and i used the k value 9 and gave me an answer 1083.3, which was the correct answer...

2. Apr 18, 2007

looks right.