The coefficient of thermal conductivity depends upon

A room is maintained at ${20^o}C$ by a heater of resistance $20$ ohm connected to $200$ volt mains. The temperature is uniform through out the room and heat is transmitted through a glass window of area $1{m^2}$ and thickness $0.2$ cm. What will be the temperature outside ....... $^oC$ ? Given that thermal conductivity $K=0.2$ for glass is and $J = 4.2 J/cal$

An ice box used for keeping eatable cold has a total wall area of $1\;metr{e^2}$ and a wall thickness of $5.0cm$. The thermal conductivity of the ice box is $K = 0.01\;joule/metre{ - ^o}C$. It is filled with ice at ${0^o}C$ along with eatables on a day when the temperature is $30°C$ . The latent heat of fusion of ice is $334 \times {10^3}joules/kg$. The amount of ice melted in one day is ........ $gms$ ($1day = 86,400\;\sec onds$) 

Two different rods $A$ and $B$ are kept as shown in figure. The ratio of thermal conductivities of $A$ and $B$ is

A slab of stone of area $0.36\;m ^2$ and thickness $0.1 \;m$ is exposed on the lower surface to steam at $100^{\circ} C$. A block of ice at $0^{\circ} C$ rests on the upper surface of the slab. In one hour $4.8\; kg$ of ice is melted. The thermal conductivity of slab is .......... $J / m / s /{ }^{\circ} C$ (Given latent heat of fusion of ice $=3.36 \times 10^5\; J kg ^{-1}$)

Three rods of equal length and cross sectional area and coefficient of thermal conductivities $K, 2K$ and $3K$ are joined as shown in figure temperature of their ends are $110\ ^oC, 20\ ^oC$ and $0\ ^oC$ respectively then temperature of junction will be ......... $^oC$