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## Homework Statement

A cubical box 22cm on a side is constructed from 1.3cm -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

rate of heat transfer : heat / delta small t = (k*A*delta big T)/ L

Where : k = characterizes the material : (in this case its concrete) : 0.8 W/m K

L = Thickness of the panels : .013m

A = cross-section area = s^2 : (.22m)^2 = .0484

## The Attempt at a Solution

100 W = ((0.8)(.22)^2(Tin - 20 C)) / .013m // the 20 C is the Tout

Tin = 53.5754 = 54 Degrees Celsius.

According to Mastering Physics this is the incorrect answer. To me it makes sense, and after reviewing my work, I cant' seem to find the error. Any help will be greatly appreciated.

-UMDstudent