Q.
Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?
A) $A\ $and $B$ have same specific heats
B) Specific heat of $A\ $is less
C) Specific heat of $B$ is less
D) Nothing can be said
Explanation
(b) According to Newton’s law of cooling, rate of cooling is given by
$\left( \frac{- dT}{dt} \right) = \frac{eA\sigma}{mc}(T^{4} - T_{0}^{4})$
where c is specific heat of material.
or $\left( \frac{- dT}{dt} \right) \propto \frac{1}{c}$
$ie.,\ $rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.