A black body at a temperature of $127°C$ radiates heat at the rate of $1 cal/cm^2 × sec$. At a temperature of $527°C$ the rate of heat radiation from the body in ($cal/cm^2 × sec$) will be
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On investigation of light from three different stars $A, B$ and $C$ , it was found that in the spectrum of $A$ the intensity of red colour is maximum, in $B$ the intensity of blue colour is maximum and in $C$ the intensity of yellow colour is maximum. From these observations it can be concluded that
A solid copper cube of edges $1\;cm$ is suspended in an evacuated enclosure. Its temperature is found to fall from ${100^o}C$ to ${99^o}C$ in $100\;s$. Another solid copper cube of edges $2\;cm$, with similar surface nature, is suspended in a similar manner. The time required for this cube to cool from ${100^o}C$ to ${99^o}C$ will be approximately ...... $\sec$
Two cylinders $P$ and $Q$ have the same length and diameter and are made of different materials having thermal conductivities in the ratio $2 : 3$ . These two cylinders are combined to make a cylinder. One end of $P$ is kept at $100°C$ and another end of $Q$ at $0°C$ . The temperature at the interface of $P$ and $Q$ is ...... $^oC$
A body of length 1m having cross sectional area $0.75\;m^2$ has heat flow through it at the rate of $ 6000\; Joule/sec$ . Then find the temperature difference if $K = 200\;J{m^{ - 1}}{K^{ - 1}}$ ...... $^oC$
Two spheres of the same material have radii $1\; m$ and $4\; m$ and temperatures $4000 \;K$ and $2000 \;K$ respectively. The ratio of the energy radiated per second by the first sphere to that by the second is
Twelve conducting rods form the riders of a uniform cube of side $'l'.$ If in steady state, $B$ and $H$ ends of the rod are at $100^o C$ and $0^o C$. Find the temperature of the junction $'A'$ ....... $^oC$
A black coloured solid sphere of radius $R$ and mass $M$ is inside a cavity with vacuum inside. The walls of the cavity are maintained at temperature $T_0$. The initial temperature of the sphere is $3T_0$. If the specific heat of the material of the sphere varies as $\alpha T^3$ per unit mass with the temperature $T$ of the sphere, where $\alpha $ is a constant, then the time taken for the sphere to cool down to temperature $2T_0$ will be ( $\sigma $ is Stefan Boltzmann constant)