Question

Two circular discs A and B with equal radii are blackened. They are heated to the same temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

Options

• A and B have the same specific heats

• Specific heat of A is less

• Specific heat of B is less

• Nothing can be said

Answer 1

Specific heat of A is less

Explanation:

From Newton's law of cooling, the rate of cooling is given by

`((-"d"θ)/("dt")) = ("eA"σ)/"mc" (θ^4 - θ_0^4)`

Where e is the specific heat of the material.

`((-"d"θ)/("dt")) ∝ 1/"c"`

−ve sign shows that temperature decreases.

⇒ For A, rate of colling `(("d"θ)/("dt"))` is large.

∴ Specific heat of A is smaller.