A body cools from ${60^o}C$ to ${50^o}C$ in $10$ minutes when kept in air at ${30^o}C$. In the next $10$ minutes its temperature will be
Medium
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(c) By Newton’s law of cooling.
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A spherical black body with a radius of $24\;cm$ radiates $440\;W$ power at $500\;K$. If the radius were halved and the temperature doubled, the power radiated in watt would be
A metal rod of length $2\, m$ has cross-sectional areas $2A$ and $A$ as shown in the following figure. The two ends are maintained at temperatures $100\,^oC$ and $70\,^oC$. The temperature of middle point $C$ is ........ $^oC$
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)
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 $K = 200\;J{m^{ - 1}}{K^{ - 1}}$ ...... $^oC$
The temperature of a piece of iron is ${27^o}C$ and it is radiating energy at the rate of $Q\;kW{m^{ - 2}}$. If its temperature is raised to ${151^o}C$, the rate of radiation of energy will become approximately ....... $Q\,kW\,{m^{ - 2}}$
Two walls of thicknesses $d_1$ and $d_2$ and thermal conductivities $k_1$ and $k_2$ are in contact. In the steady state, if the temperatures at the outer surfaces are ${T_1}$ and ${T_2}$, the temperature at the common wall is
A metallic rod of cross-sectional area $9.0\,\,cm^2$ and length $0.54 \,\,m$, with the surface insulated to prevent heat loss, has one end immersed in boiling water and the other in ice-water mixture. The heat conducted through the rod melts the ice at the rate of $1 \,\,gm$ for every $33 \,\,sec$. The thermal conductivity of the rod is ....... $ Wm^{-1} K^{-1}$
The two ends of a metal rod are maintained at temperatures $100 ^o C$ and $110^o C$. The rate of heat flow in the rod is found to be $4.0\ J/s$. If the ends are maintained at temperatures $200^o\ C$ and $210^o\ C$, the rate of heat flow will be.... $J/s$