(D) The heat produced by the heater per unit time is $P = \frac{V^2}{R} = \frac{200^2}{20} = 2000 \ W = 2000 \ J/s$.The heat conducted through the gla

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(D) The heat produced by the heater per unit time is $P = \frac{V^2}{R} = \frac{200^2}{20} = 2000 \ W = 2000 \ J/s$.The heat conducted through the glass window per unit time is given by $H = \frac{K A (T_{in} - T_{out})}{d}$.Here, $K = 0.2 \ W/(m \cdot K)$, $A = 1 \ m^2$, $d = 0.2 \ cm = 0.002 \ m$, and $T_{in} = 20^{\circ}C$.Equating the heat produced to the heat conducted: $2000 = \frac{0.2 \times 1 \times (20 - T_{out})}{0.002}$.$2000 = 100 \times (20 - T_{out})$.$20 = 20 - T_{out}$.$T_{out} = 0^{\circ}C$. Since this result is not among the options, the correct choice is $D$.

Class 11 Physics 10-2.Heat Transfer Heat Conduction and Thermal Conductivity

Medium

$A$ room is maintained at $20^{\circ}C$ by a heater of resistance $20 \ \Omega$ connected to $200 \ V$ mains. The temperature is uniform throughout the room and heat is transmitted through a glass window of area $1 \ m^2$ and thickness $0.2 \ cm$. What will be the temperature outside in $^{\circ}C$? Given that thermal conductivity $K = 0.2 \ J/(s \cdot m \cdot K)$ for glass and $J = 4.2 \ J/cal$.

IIT 1978 All IIT

A
$15.24$
B
$15.00$
C
$24.15$
D
None of the above

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10-2.Heat Transfer

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Heat Conduction and Thermal Conductivity

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Two metal rods $1$ and $2$ have the same length and the same temperature difference at their ends. Their thermal conductivities are $K_1$ and $K_2$ and their cross-sectional areas are $A_1$ and $A_2$ respectively. The condition for the same rate of heat flow in them is ........

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$A$ thermocol box has a total wall area (including the lid) of $1.0 \,m^2$ and wall thickness of $3 \,cm$. It is filled with ice at $0^{\circ} C$. If the average temperature outside the box is $30^{\circ} C$ throughout the day, the amount of ice that melts in one day is (Given: $K_{\text{thermocol}} = 0.03 \,W/mK$, $L_{\text{fusion(ice)}} = 3.00 \times 10^5 \,J/kg$) (in $\,kg$)

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Two spheres of different materials,one with double the radius and one-fourth wall thickness of the other,are filled with ice. If the time taken for complete melting of ice in the large radius sphere is $25 \ minutes$ and that for the smaller one is $16 \ minutes$,the ratio of thermal conductivities of the materials of the larger sphere to the smaller sphere is:

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$A$ cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat $Q$ in time $t$. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod,when placed in thermal contact with the two reservoirs in time $t$?

MediumAIPMT 2010

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Two sheets of thickness $d$ and $2d$ and the same area are touching each other on their faces. The temperatures $T_A$,$T_B$,and $T_C$ shown are in a geometric progression with a common ratio $r = 2$. Then,the ratio of the thermal conductivity of the thinner sheet to the thicker sheet is:

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Two metal rods $1$ and $2$ have the same length and the same temperature difference at their ends. Their thermal conductivities are $K_1$ and $K_2$ and their cross-sectional areas are $A_1$ and $A_2$ respectively. The condition for the same rate of heat flow in them is ........

Two sheets of thickness $d$ and $2d$ and the same area are touching each other on their faces. The temperatures $T_A$,$T_B$,and $T_C$ shown are in a geometric progression with a common ratio $r = 2$. Then,the ratio of the thermal conductivity of the thinner sheet to the thicker sheet is:

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