Heat TransferMedium
Question
A Sphere of ice at 0oC having initial radius R is placed in an environ melts having ambient temperature > 0oC. The ice melts uniformly, such that shape remains spherical. After a time ′t′ the radius of the of the sphere has reduced to r. Which graph best depicts r(t)
Options
A.
B.
C.
D.
Solution
Heat lost
= σA (T4 - T04) = - σ4πr2 (T04 - T4)
=
= ρL 
ρL4πr2
⇒ - σ4πρ2 (T04 - T4) = σL4πr2
⇒ radius decrease with time
= σA (T4 - T04) = - σ4πr2 (T04 - T4)
=
= ρL ρL4πr2⇒ - σ4πρ2 (T04 - T4) = σL4πr2
⇒ radius decrease with time
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