Transmission Of Heat Question 190
Question: A calorimeter of mass 0.2 kg and specific heat 900 J/kg-K. Containing 0.5 kg of a liquid of specific heat 2400J /kg-K. Its temperature falls from $ 60^{o}C,\text{to},,\text{5}{{\text{5}}^{\text{o}}}C $ in one minute. The rate of cooling is
[MP PET 2003]
Options:
A) 5 J/s
B) 15 J/s
C) 100 J/s
D) 115 J/s
Show Answer
Answer:
Correct Answer: D
Solution:
Rate of cooling (here it is rate of loss of heat) $ \frac{dQ}{dt}=(mc+W)\frac{d\theta }{dt}=(m _{l}c _{l}+m _{c}c _{c})\frac{d\theta }{dt} $
Therefore $ \frac{dQ}{dt}=(0.5\times 2400+0.2\times 900)( \frac{60-55}{60} ) $
$ =115\ \frac{J}{\sec } $ .
BETA
