- #1
composyte
- 21
- 6
Homework Statement
A cubical box 19cm on a side is constructed from 1.4cm -thick concrete panels. A 100 W lightbulb is sealed inside the box. What is the air temperature inside the box when the light is on if the surrounding air temperature is 20 ∘ C ?
Homework Equations
E_th=W+Q
Q_net=Q_1+Q_2+...
E_th=N*C_v (deltaT)
(Q/delta(t))=e*(sigma)*A*T^4
The Attempt at a Solution
okay so I am thinking that I should find Q_net which will be equal to E_th to find the final temperature of the air.. And so I would use the (Q/delta(t)) equation to find the radiation emitted from the lightbulb and the radiation emitted from the concrete panels...My problem is the question doesn't give the emissivity of the concrete and nor does it say what the initial temperature for the air should be. Because of this I feel like my answer is entirely on the wrong path..Either that or the question is just expecting you to make a lot of assumptions..any help??