One likes to sit under sunshine in winter season, because
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(a)Heat flows from hot air to cold body so person feels comfort.
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A black body at a temperature of ${227^o}C$ radiates heat energy at the rate of $5 cal/cm^2-sec$. At a temperature of ${727^o}C$, the rate of heat radiated per unit area in $cal/cm^2$ will be
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......... $^oC$
The sun radiates electromagnetic energy at the rate of $3.9 \times 10^{26}\,W$. It's radius is $6.96 \times 10^8\,m$. The intensity of sun light at the solar surface will be (in $W/m^2$)
Three rods of the same dimension have thermal conductivities $3K$ , $2K$ and $K$ . They are arranged as shown in fig. Given below, with their ends at $100^oC, 50^oC $and $20^oC$. The temperature of their junction is ......... $^oC$
Three rods of same material, same area of crosssection but different lengths $10 \,cm , 20 \,cm$ and $30 \,cm$ are connected at a point as shown. What is temperature of junction $O$ is ......... $^{\circ} C$
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 ....... $\overset{o}{\mathop{A}}\,$
The coefficient of linear expansion of brass and steel are ${\alpha _1}$ and ${\alpha _2}$. If we take a brass rod of length ${l_1}$ and steel rod of length ${l_2}$ at $0°C$, their difference in length $({l_2} - {l_1})$ will remain the same at a temperature if
Two metal rods $1$ and $2$ of same lengths have same temperature difference between their ends. Their thermal conductivities are $K_1$ and $K_2$ and cross sectional areas $A_1$ and $A_2$ , respectively. If the rate of heat conduction in $1$ is four times that in $2$, then
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 $B$ ?