Why it is more hotter for same distance over the top of a candle than it in the side of its flame?
A
Conduction of heat in air is upward
B
Heat is maximum radiated in upward direction
C
Radiation and conduction both contribute in transferring heat upwards
D
Convection takes more heat in upward direction
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D
Convection takes more heat in upward direction
d (d)
On the sides heating is only due to Radiation but over the top heating is due to Radiation as well as convection.
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A copper pipe of length $10 \,m$ carries steam at temperature $110^{\circ} C$. The outer surface of the pipe is maintained at a temperature $10^{\circ} C$. The inner and outer radii of the pipe are $2 \,cm$ and $4 \,cm$, respectively. The thermal conductivity of copper is $0.38 kW / m /{ }^{\circ} C$. In the steady state, the rate at which heat flows radially outward through the pipe is closest to ............. $\,kW$
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The only possibility of heat flow in a thermos flask is through its cork which is $75 cm^2$ in area and $5 cm$ thick. Its thermal conductivity is $0.0075 cal/cmsec^oC$. The outside temperature is$ 40^oC$ and latent heat of ice is $80 cal g^{-1}$. Time taken by $500 g$ of ice at $0^oC$ in the flask to melt into water at $0^oC$ is ....... $hr$
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