Two bars of thermal conductivities $K$ and $3K$ and lengths $1\,\, cm$ and $2\,\, cm$ respectively have equal cross-sectional area, they are joined lengths wise as shown in the figure. If the temperature at the ends of this composite bar is $0\,^oC$ and $100\,^oC$ respectively (see figure), then the temperature $\varphi $ of the interface is......... $^oC$
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A cylinder of radius $R$ is surrounded by a cylindrical shell of inner radius $R$ and outer radius $2R$. The thermal conductivity of the material of the inner cylinder is $K_1$ and that of the outer cylinder is $K_2$. Assuming no loss of heat, the effective thermal conductivity of the system for heat flowing along the length of the cylinder is
A body takes $T$ minutes to cool from ${62^o}C$ to ${61^o}C$ when the surrounding temperature is ${30^o}C$. The time taken by the body to cool from ${70^o}$ to $({A_1}\,{\rm{and }}{A_{\rm{2}}})$ is
If the radius of a star is $R$ and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is Q? ( $\sigma$ stands for Stefan's constant.)
The temperature of a liquid drops from $365K$ to $361 K$ in $2$ minutes. Find the time during which temperature of the liquid drops from $344\;K$ to $342K$. Temperature of room is $293\;K$ ....... $\sec$
Solar radiation emitted by sun resembles that emitted by a black body at a temperature of $6000 K$ . Maximum intensity is emitted at a wavelength of about $4800Å$ . If the sun were to cool down from $6000 K$ to $3000 K$ then the peak intensity would occur at a wavelength ....... $\overset{o}{\mathop{A}}\,$
Column $I$ gives some devices and Column $II$ gives some process on which the functioning of these devices depend. Match the devices in Column $I$ with the processes in Column $II$ and indicate your answer by darkening appropriate bubbles in the $4 \times 4$ matrix given in the $ORS$.
Two spherical bodies $\mathrm{A}$ (radius $6 \mathrm{~cm}$ ) and $\mathrm{B}$ (radius $18 \mathrm{~cm}$ ) are at temperature $\mathrm{T}_1$ and $\mathrm{T}_2$, respectively. The maximum intensity in the emission spectrum of $\mathrm{A}$ is at $500 \mathrm{~nm}$ and in that of $\mathrm{B}$ is at $1500 \mathrm{~nm}$. Considering them to be black bodies, what will be the ratio of the rate of total energy radiated by $A$ to that of $B$ ?