A lead sphere has three times the radius of an iron sphere. Both are heated to the same temperature and cool under identical conditions. Specific heats: iron 450 J/kg K, lead 130 J/kg K. Specific grav

Question

A lead sphere has three times the radius of an iron sphere. Both are heated to the same temperature and cool under identical conditions. Specific heats: iron 450 J/kg K, lead 130 J/kg K. Specific gravities: iron 7.8, lead 11.3. Find the ratio (iron : lead) of the initial rates of fall of temperature.

Answer:

1.26

Solution:

Rate of fall $\propto \frac{1}{r ρ c}$ . Iron : lead = $\frac{3 \times 11.3 \times 130}{7.8 \times 450} = 1.26$ .

TestHub · Accepted Answer

Rate of fall ∝ r ρ c 1 ​ . Iron : lead = 7.8 × 450 3 × 11.3 × 130 ​ = 1.26 .

Physics - Heat & Thermo Question with Solution | TestHub

Doubts & Discussion