Question

Two solid spheres, of radii R₁ and R₂ are made of the same material and have similar surfaces. The spheres are raised to the same temperature and then allowed to cool under identical conditions. Assuming spheres to be perfect conductors of heat, their initial rates of loss of heat are -

• A. $R_{1}^{2}/R_{2}^{2}$
• B. R₁/R₂
• C. R₂/R₁
• D. $R_{2}^{2}/R_{1}^{2}$

Answer 1

Answer: (A)

$R_{1}^{2}/R_{2}^{2}$

Answer 2

Rate of hoss of heat

= $\frac{\sigma\pi^{4} \times A_{1} \times e_{1}}{\sigma\pi^{4} \times A_{2} \times e_{2}}$ = $\frac{R_{1}^{2}}{R_{2}^{2}}$ [\ e₁ = e₂]