00. Conduction
Heat Transfer

149317 A uniform copper rod of $50 \mathrm{~cm}$ length is insulated on the sides and has its ends exposed to ice and steam respectively. If there is a layer of water $1 \mathrm{~mm}$ thick at each end, the temperature gradient (in ${ }^{\circ} \mathrm{C} \mathrm{m}^{-1}$ ) in the bar is (assume that the thermal conductivity of copper is $400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ and water is $0.4 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ )

1 60
2 40
3 50
4 55
5 65
Heat Transfer

149318 A partition wall has two layers of different materials $A$ and $B$ in contact with each other. They have the same thickness but the thermal conductivity of layer $A$ is twice that of layer $B$. At steady state if the temperature difference across the layer $B$ is $50 \mathrm{~K}$, then the corresponding difference across the layer $A$ is

1 $50 \mathrm{~K}$
2 $12.5 \mathrm{~K}$
3 $25 \mathrm{~K}$
4 $60 \mathrm{~K}$
5 $6.25 \mathrm{~K}$
Heat Transfer

149319 Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is

1 $45^{\circ} \mathrm{C}$
2 $90^{\circ} \mathrm{C}$
3 $30^{\circ} \mathrm{C}$
4 $20^{\circ} \mathrm{C}$
5 $60^{\circ} \mathrm{C}$
Heat Transfer

149320 An ice box made of Styrofoam (Thermal conductivity $=0.01 \mathrm{Jm}^{-1} \mathrm{~s}^{-1} \mathrm{~K}^{-1}$ ) is used to keep liquids cool. It has a total wall area including lid of $0.8 \mathrm{~m}^{2}$ and wall thickness of $2.0 \mathrm{~cm}$. A bottle of water is placed in the box and filled with ice. If the outside temperature is $30^{\circ} \mathrm{C}$ the rate of flow of heat into the box is: (in $\mathrm{J}^{-1}$ ) :

1 16
2 14
3 12
4 10
5 8
Heat Transfer

149322 In a room where the temperature is $30^{\circ} \mathrm{C}$ a body cools from $61^{\circ} \mathrm{C}$ to $59^{\circ} \mathrm{C}$ in 4 minutes. The time taken by the body to cool from $51^{\circ} \mathrm{C}$ to $49^{\circ} \mathrm{C}$ will be about

1 5 minutes
2 8 minutes
3 4 minutes
4 6 minutes
Heat Transfer

149317 A uniform copper rod of $50 \mathrm{~cm}$ length is insulated on the sides and has its ends exposed to ice and steam respectively. If there is a layer of water $1 \mathrm{~mm}$ thick at each end, the temperature gradient (in ${ }^{\circ} \mathrm{C} \mathrm{m}^{-1}$ ) in the bar is (assume that the thermal conductivity of copper is $400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ and water is $0.4 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ )

1 60
2 40
3 50
4 55
5 65
Heat Transfer

149318 A partition wall has two layers of different materials $A$ and $B$ in contact with each other. They have the same thickness but the thermal conductivity of layer $A$ is twice that of layer $B$. At steady state if the temperature difference across the layer $B$ is $50 \mathrm{~K}$, then the corresponding difference across the layer $A$ is

1 $50 \mathrm{~K}$
2 $12.5 \mathrm{~K}$
3 $25 \mathrm{~K}$
4 $60 \mathrm{~K}$
5 $6.25 \mathrm{~K}$
Heat Transfer

149319 Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is

1 $45^{\circ} \mathrm{C}$
2 $90^{\circ} \mathrm{C}$
3 $30^{\circ} \mathrm{C}$
4 $20^{\circ} \mathrm{C}$
5 $60^{\circ} \mathrm{C}$
Heat Transfer

149320 An ice box made of Styrofoam (Thermal conductivity $=0.01 \mathrm{Jm}^{-1} \mathrm{~s}^{-1} \mathrm{~K}^{-1}$ ) is used to keep liquids cool. It has a total wall area including lid of $0.8 \mathrm{~m}^{2}$ and wall thickness of $2.0 \mathrm{~cm}$. A bottle of water is placed in the box and filled with ice. If the outside temperature is $30^{\circ} \mathrm{C}$ the rate of flow of heat into the box is: (in $\mathrm{J}^{-1}$ ) :

1 16
2 14
3 12
4 10
5 8
Heat Transfer

149322 In a room where the temperature is $30^{\circ} \mathrm{C}$ a body cools from $61^{\circ} \mathrm{C}$ to $59^{\circ} \mathrm{C}$ in 4 minutes. The time taken by the body to cool from $51^{\circ} \mathrm{C}$ to $49^{\circ} \mathrm{C}$ will be about

1 5 minutes
2 8 minutes
3 4 minutes
4 6 minutes
Heat Transfer

149317 A uniform copper rod of $50 \mathrm{~cm}$ length is insulated on the sides and has its ends exposed to ice and steam respectively. If there is a layer of water $1 \mathrm{~mm}$ thick at each end, the temperature gradient (in ${ }^{\circ} \mathrm{C} \mathrm{m}^{-1}$ ) in the bar is (assume that the thermal conductivity of copper is $400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ and water is $0.4 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ )

1 60
2 40
3 50
4 55
5 65
Heat Transfer

149318 A partition wall has two layers of different materials $A$ and $B$ in contact with each other. They have the same thickness but the thermal conductivity of layer $A$ is twice that of layer $B$. At steady state if the temperature difference across the layer $B$ is $50 \mathrm{~K}$, then the corresponding difference across the layer $A$ is

1 $50 \mathrm{~K}$
2 $12.5 \mathrm{~K}$
3 $25 \mathrm{~K}$
4 $60 \mathrm{~K}$
5 $6.25 \mathrm{~K}$
Heat Transfer

149319 Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is

1 $45^{\circ} \mathrm{C}$
2 $90^{\circ} \mathrm{C}$
3 $30^{\circ} \mathrm{C}$
4 $20^{\circ} \mathrm{C}$
5 $60^{\circ} \mathrm{C}$
Heat Transfer

149320 An ice box made of Styrofoam (Thermal conductivity $=0.01 \mathrm{Jm}^{-1} \mathrm{~s}^{-1} \mathrm{~K}^{-1}$ ) is used to keep liquids cool. It has a total wall area including lid of $0.8 \mathrm{~m}^{2}$ and wall thickness of $2.0 \mathrm{~cm}$. A bottle of water is placed in the box and filled with ice. If the outside temperature is $30^{\circ} \mathrm{C}$ the rate of flow of heat into the box is: (in $\mathrm{J}^{-1}$ ) :

1 16
2 14
3 12
4 10
5 8
Heat Transfer

149322 In a room where the temperature is $30^{\circ} \mathrm{C}$ a body cools from $61^{\circ} \mathrm{C}$ to $59^{\circ} \mathrm{C}$ in 4 minutes. The time taken by the body to cool from $51^{\circ} \mathrm{C}$ to $49^{\circ} \mathrm{C}$ will be about

1 5 minutes
2 8 minutes
3 4 minutes
4 6 minutes
Heat Transfer

149317 A uniform copper rod of $50 \mathrm{~cm}$ length is insulated on the sides and has its ends exposed to ice and steam respectively. If there is a layer of water $1 \mathrm{~mm}$ thick at each end, the temperature gradient (in ${ }^{\circ} \mathrm{C} \mathrm{m}^{-1}$ ) in the bar is (assume that the thermal conductivity of copper is $400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ and water is $0.4 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ )

1 60
2 40
3 50
4 55
5 65
Heat Transfer

149318 A partition wall has two layers of different materials $A$ and $B$ in contact with each other. They have the same thickness but the thermal conductivity of layer $A$ is twice that of layer $B$. At steady state if the temperature difference across the layer $B$ is $50 \mathrm{~K}$, then the corresponding difference across the layer $A$ is

1 $50 \mathrm{~K}$
2 $12.5 \mathrm{~K}$
3 $25 \mathrm{~K}$
4 $60 \mathrm{~K}$
5 $6.25 \mathrm{~K}$
Heat Transfer

149319 Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is

1 $45^{\circ} \mathrm{C}$
2 $90^{\circ} \mathrm{C}$
3 $30^{\circ} \mathrm{C}$
4 $20^{\circ} \mathrm{C}$
5 $60^{\circ} \mathrm{C}$
Heat Transfer

149320 An ice box made of Styrofoam (Thermal conductivity $=0.01 \mathrm{Jm}^{-1} \mathrm{~s}^{-1} \mathrm{~K}^{-1}$ ) is used to keep liquids cool. It has a total wall area including lid of $0.8 \mathrm{~m}^{2}$ and wall thickness of $2.0 \mathrm{~cm}$. A bottle of water is placed in the box and filled with ice. If the outside temperature is $30^{\circ} \mathrm{C}$ the rate of flow of heat into the box is: (in $\mathrm{J}^{-1}$ ) :

1 16
2 14
3 12
4 10
5 8
Heat Transfer

149322 In a room where the temperature is $30^{\circ} \mathrm{C}$ a body cools from $61^{\circ} \mathrm{C}$ to $59^{\circ} \mathrm{C}$ in 4 minutes. The time taken by the body to cool from $51^{\circ} \mathrm{C}$ to $49^{\circ} \mathrm{C}$ will be about

1 5 minutes
2 8 minutes
3 4 minutes
4 6 minutes
Heat Transfer

149317 A uniform copper rod of $50 \mathrm{~cm}$ length is insulated on the sides and has its ends exposed to ice and steam respectively. If there is a layer of water $1 \mathrm{~mm}$ thick at each end, the temperature gradient (in ${ }^{\circ} \mathrm{C} \mathrm{m}^{-1}$ ) in the bar is (assume that the thermal conductivity of copper is $400 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ and water is $0.4 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ )

1 60
2 40
3 50
4 55
5 65
Heat Transfer

149318 A partition wall has two layers of different materials $A$ and $B$ in contact with each other. They have the same thickness but the thermal conductivity of layer $A$ is twice that of layer $B$. At steady state if the temperature difference across the layer $B$ is $50 \mathrm{~K}$, then the corresponding difference across the layer $A$ is

1 $50 \mathrm{~K}$
2 $12.5 \mathrm{~K}$
3 $25 \mathrm{~K}$
4 $60 \mathrm{~K}$
5 $6.25 \mathrm{~K}$
Heat Transfer

149319 Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is

1 $45^{\circ} \mathrm{C}$
2 $90^{\circ} \mathrm{C}$
3 $30^{\circ} \mathrm{C}$
4 $20^{\circ} \mathrm{C}$
5 $60^{\circ} \mathrm{C}$
Heat Transfer

149320 An ice box made of Styrofoam (Thermal conductivity $=0.01 \mathrm{Jm}^{-1} \mathrm{~s}^{-1} \mathrm{~K}^{-1}$ ) is used to keep liquids cool. It has a total wall area including lid of $0.8 \mathrm{~m}^{2}$ and wall thickness of $2.0 \mathrm{~cm}$. A bottle of water is placed in the box and filled with ice. If the outside temperature is $30^{\circ} \mathrm{C}$ the rate of flow of heat into the box is: (in $\mathrm{J}^{-1}$ ) :

1 16
2 14
3 12
4 10
5 8
Heat Transfer

149322 In a room where the temperature is $30^{\circ} \mathrm{C}$ a body cools from $61^{\circ} \mathrm{C}$ to $59^{\circ} \mathrm{C}$ in 4 minutes. The time taken by the body to cool from $51^{\circ} \mathrm{C}$ to $49^{\circ} \mathrm{C}$ will be about

1 5 minutes
2 8 minutes
3 4 minutes
4 6 minutes