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10-2.Transmission of Heat
hard
ગરમ પાણીનું તાપમાન $ {62^o}C $ થી $ {50^o}C $ થતા $10$ min લાગે છે,અને તાપમાન $ {50^o}C $ થી $ {42^o} $ થતા $10$ min લાગે છે.તો વાતાવરણનું તાપમાન ......... $^oC$ હશે.
A
$30$
B
$36$
C
$26$
D
$20$
Solution
(c) $\frac{{{\theta _1} – {\theta _2}}}{t} = K\left[ {\frac{{{\theta _1} + {\theta _2}}}{2} – {\theta _0}} \right]$
In the first 10 minute
$\frac{{62 – 50}}{{10}} = K\,\left[ {\frac{{62 + 50}}{2} – {\theta _0}} \right]$
==> $1.2 = \,K\,[56 – {\theta _0}]$ …. $(i)$
$\frac{{50 – 42}}{{10}} = K\,\left[ {\frac{{50 + 42}}{2} – {\theta _0}} \right]$
==> $0.8 = \,K\,[46 – {\theta _0}]$ …. $(ii)$
from equations $(i)$ and $(ii)$
$\frac{{1.2}}{{0.8}} = \frac{{(56 – {\theta _0})}}{{(46 – {\theta _0})}}$
==> ${\theta _0} = 26^\circ C$
Standard 11
Physics
