A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of

cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of

5.0 cm. If 4.0 kg of ice is put in the box, what is the amount of ice remaining after 6 h?

The outside temperature is 45 °C, and the coefficient of thermal conductivity of thermacole is $0.01 J s^{-1} m^{-1} K^{-1}.$$\left[Heat of fusion of water=335\times {10}^3 J k{g}^{-1}\right]$

1. 2.9 kg
2. 3.1 kg
3. 3.7 kg
4 4.10 kg

A brass boiler has a base area of 0.15 $m^2$ and a thickness of 1.0 cm. It boils water at a rate of 6.0 kg/min when placed on a gas stove. What is the temperature of the part of the flame in contact with the boiler?
(Thermal conductivity of brass = $109 J s^{-1} m^{-1} K^{-1}$, the heat of vaporization of water =$2256\times {10}^3 J/kg$.)
1. 237.98°C
2. 150°C
3. 137.98°C
4. 100°C