Question

The rate of cooling at 600 K, if surrounding temperature is 300 K is H. The rate of cooling at 900 K is

• A. $\frac{16}{3}H$
• B. 2 H
• C. 3 H
• D. $\frac{2}{3}H$

Answer 1

Answer: (A)

$\frac{16}{3}H$

Answer 2

By Stefan’s law, Rate of cooling,

$H \propto (T^{4} - T_{0}^{4})$

$\therefore\frac{H`}{H} = \frac{(900)^{4} - (300)^{4}}{(600)^{4}(300)^{4}} = \frac{9^{4} - 3^{4}}{6^{4} - 3^{4}} = \frac{3^{4}(3^{4} - 1)}{3^{4}(2^{4} - 1)}$

$\therefore H` = \frac{16}{3}H$