Question

Two circular discs A and B with equal radii are blackened. They are heated to same 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

Answer 1

Answer: (B)

From to Newton's law of cooling, rate of cooling is given by
$\left(\frac{-d\theta }{dt}\right)=\frac{eA\sigma }{mc}\left({\theta }^4-{\theta }_0^4\right)$
Where, $e$ is specific heat of material.
$\left(\frac{-d\theta }{dt}\right)\propto \frac{1}{c}$
-ve sign shows that temperature decreases.
$\Rightarrow$ For $A,$ rate of colling $\left(\frac{d\theta }{dt}\right)$ is large
$\therefore$ Specific heat of $A$ is smaller