Transmission Of Heat Question 236
Question: Two spheres of same material have radius 1m and 4 m and temperature 4000K and 2000K respectively. The energy radiated per second by the first sphere is
[Pb. PMT 2002]
Options:
A) Greater than that by the second one
B) Less than that by the second
C) Equal in both cases
D) The information is incomplete
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Answer:
Correct Answer: C
Solution:
Energy radiated per sec $ \frac{Q}{t}=P=A\varepsilon \sigma T^{4} $
$ P\propto r^{2}T^{4}\Rightarrow \frac{P _{2}}{P _{1}}=\frac{r _{2}^{2}}{r _{1}^{ 2}}.\frac{T _{2}^{4}}{T _{1}^{4}}=\frac{4^{2}}{1^{2}}\times {{( \frac{4000}{2000} )}^{4}}=256 $
BETA
