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Bottom of a lake is at $0^{\circ} C$ and atmospheric temperature is $-20^{\circ} C$. If $1 cm$ ice is formed on the surface in $24 \,h$, then time taken to form next $1 \,cm$ of ice is ......... $h$
A small object is placed at the center of a large evacuated hollow spherical container. Assume that the container is maintained at $0 K$. At time $t =0$, the temperature of the object is $200 K$. The temperature of the object becomes $100 K$ at $t = t _1$ and $50 K$ at $t = t _2$. Assume the object and the container to be ideal black bodies. The heat capacity of the object does not depend on temperature. The ratio $\left( t _2 / t _1\right)$ is. . . . .
Which of the following graphs correctly represents the relation between ln $E$ and ln $T$ where $E$ is the amount of radiation emitted per unit time from unit area of a body and $T$ is the absolute temperature
A calorimeter of mass $0.2$ kg and specific heat $900 J/kg-K$ . Containing $0.5$ kg of a liquid of specific heat $2400J /kg-K$ . Its temperature falls from ${60^o}C\,{\rm{to}}\,\,{\rm{5}}{{\rm{5}}^{\rm{o}}}C$ in one minute. The rate of cooling is ....... $J/s$
In $5\, minutes,$ a body cools from $75^{\circ} {C}$ to $65^{\circ} {C}$ at room temperature of $25^{\circ} {C}$. The temperature of body at the end of next $5\, minutes$ is $......\,{ }^{\circ} {C} .$
Heat is flowing through a conductor of length l from $x = 0$ to $x = l$ . If its thermal resistance per unit length is uniform, which of the following graphs is correct
Hot water cools from $60\,^oC$ to $50\,^oC$ in the first $10\,minutes$ and to $42\,^oC$ in the next $10\,minutes.$ The temperature of the surroundings is ...... $^oC$
A black body at a temperature of $1640 K$ has the wavelength corresponding to maximum emission equal to $1.75$ $\mu $. Assuming the moon to be a perfectly black body, the temperature of the moon, if the wavelength corresponding to maximum emission is $ 14.35$ $\mu $ is ...... $K$
Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity $K _{1}, K _{2},$ and $K _{3}$, respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at $100^{\circ} C$ and the ther at $0^{\circ} C$ (see figure). If the joints of the rod are at $70^{\circ} C$ and $20^{\circ} C$ in steady state and there is no loss of energy from the surface of the rod, the correct relationship between $K _{1}, K _{2}$ and $K _{3}$ is