(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 2 Thermal Properties of Matter: 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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2 Thermal Properties of Matter: Heat Transfer

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Heat Conduction and Thermal Conductivity

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IIT 1978 Paper All IIT years →

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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Three rods of the same dimensions have thermal conductivities $3k, 2k$ and $k$. They are arranged as shown,with their ends at $100\,^{\circ}C, 50\,^{\circ}C$ and $0\,^{\circ}C$. The temperature of their junction is

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Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio $1:2$ and their lengths are in the ratio $2:1$. If the temperature difference between their ends is the same,then the ratio of the amounts of heat conducted through per unit time will be

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One end of a copper rod of length $1.0 \; m$ and area of cross-section $10^{-3} \; m^2$ is immersed in boiling water and the other end in ice. If the coefficient of thermal conductivity of copper is $92 \; cal/(m \cdot s \cdot ^\circ C)$ and the latent heat of ice is $8 \times 10^4 \; cal/kg$,then the amount of ice which will melt in one minute is:

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What properties should a material used for making a cooking pot possess? ($K =$ thermal conductivity,$S =$ specific heat capacity)

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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:

Three rods of the same dimensions have thermal conductivities $3k, 2k$ and $k$. They are arranged as shown,with their ends at $100\,^{\circ}C, 50\,^{\circ}C$ and $0\,^{\circ}C$. The temperature of their junction is

Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio $1:2$ and their lengths are in the ratio $2:1$. If the temperature difference between their ends is the same,then the ratio of the amounts of heat conducted through per unit time will be

What properties should a material used for making a cooking pot possess? ($K =$ thermal conductivity,$S =$ specific heat capacity)

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