Calculate the surface temperature of the planet, if the energy radiated by unit area in unit time is $5.67\times10^4\, watt$ : (Planet may be assumed to black body)
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The outer faces of a rectangular slab made of equal thickness of iron and brass are maintained at $100^{\circ} C$ and $0^{\circ} C$ respectively. The temperature at the interface is ........... $^{\circ} C$ (Thermal conductivity of iron and brass are $0.2$ and $0.3$ respectively.)
The 'Kangri' is an earthen pot used to stay warm in Kashmir during the winter months. Assume that the 'Kangri' is spherical and of surface area $7 \times 10^{-2} \,m ^{2}$. It contains $300 g$ of a mixture of coal, wood and leaves with calorific value of $30 \,kJ / g$ (and provides heat with $10 \%$ efficiency). The surface temperature of the 'Kangri' is $60^{\circ} C$ and the room temperature is $0^{\circ} C$. Then, a reasonable estimate for the duration $t$ (in h) that the 'Kangri' heat will last is (take the 'Kangri' to be a black body)
Liquid cools from $50^oC$ to $45^oC$ in $5\ minutes$ and from $45^oC$ to $41.5^oC$ in the next $5\ minutes$.The temperature of the surrounding is ......... $^oC$
The absolute temperatures of two black bodies are $2000 K$ and $3000 K$ respectively. The ratio of wavelengths corresponding to maximum emission of radiation by them will be
Instantaneous temperature difference between cooling body and the surroundings obeying Newton's law of cooling is $\theta$. Which of the following represents the variation of $\ln \theta$ with time $t$ ?
Two vessels of different materials are similar in size in every respect. The same quantity of ice filled in them gets melted in $20$ minutes and $30$ minutes. The ratio of their thermal conductivities will be
Wein's constant is $2892 \times {10^{ - 6}}$$MKS$ unit and the value of ${\lambda _m}$ from moon is $14.46$ microns. What is the surface temperature of moon ...... $K$