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A solid sphere has a temperature of 614 K. The sphere is melted down and recast into a cube that has the same emissivity and emits the same radiant power as the sphere. What is the cube's temperature in kelvins?

Respuesta :

Answer:581.87 K

Explanation:

Given

Sphere is melted to form a square

Let the radius of sphere be r and square has a side a

Therefore

[tex]\frac{4\pi}{3}r^3=a^3[/tex]

Surface area of sphere [tex]A_s=4\pi r^2[/tex]

Surface area of cube [tex]A_c=6a^2[/tex]

Total emmisive remains same

Thus [tex]P=A\epsilon \sigma T^4[/tex]

[tex]A_sT_s^4=A_cT_c^4[/tex]

[tex]\frac{T_c^4}{T_s^4}=\frac{A_s}{A_c}[/tex]

[tex]\frac{T_c^4}{T_s^4}=\frac{1}{2}\times \left ( \frac{4\pi}{3}\right )^{\frac{1}{3}}[/tex]

[tex]\frac{T_c}{T_s}=\frac{1}{2^{0.25}}\times \left ( \frac{4\pi}{3}\right )^{\frac{1}{12}}[/tex]

[tex]T_c=T_s\times \frac{1}{2^{0.25}}\times \left ( \frac{4\pi}{3}\right )^{\frac{1}{12}}[/tex]

[tex]T_c=614\times \frac{1.12679}{1.189}[/tex]

[tex]T_c=581.87 K[/tex]