149369
The two ends of a rod of length $L$ and a uniform cross sectional area $A$ are kept at two temperatures $T_{1}$ and $T_{2}\left(T_{1}>T_{2}\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$ through the rod in a steady state is given by:
C Rate of heat transfer through the rod of length $\mathrm{L}$ and uniform cross-sectional area $\mathrm{A}$ and temperatures $\mathrm{T}_{1}$ and $\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)$ in steady state. Here temperature difference $(\Delta \mathrm{T})=\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)$ The rate of heat transfer $(\mathrm{dQ} / \mathrm{dt})$ is given by: $\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\Delta \mathrm{T}}{\mathrm{R}}$ Since, $\quad \mathrm{R}=\frac{\rho \mathrm{L}}{\mathrm{A}}$ $\therefore \quad \frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{kA}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{L}} \quad\left(\because \mathrm{k}=\frac{1}{\rho}\right)$
AIIMS-26.05.2019(M) Shift-1
Heat Transfer
149370
Thermal conductivity of a material in CGS system is 0.4. In steady state, the rate of flow of heat is $10 \mathrm{cal} / \mathrm{s}-\mathrm{cm}^{2}$. The thermal gradient will be-
149362
Assertion: Two thin blankets put together are warmer than a single blanket of double the thickness. Reason: Thickness increases because of air layer enclosed between the two blankets.
1 If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
2 If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
3 If Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
Explanation:
C Two thin blankets put together are warmer than a single blanket of double the thickness because air is trapped in the space between two thin blankets. Since, air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.
AIIMS-2010
Heat Transfer
149364
Assertion: Woolen clothes keep the body warm in winter. Reason: Air is a bad conductor of heat.
1 If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
2 If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
3 If the Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
5 If the Assertion is incorrect but the Reason is correct.
Explanation:
A Woolen clothes keep the body warm in winter because air particle trapped inside the woolen clothes, As we know, air is bad conductor of heat due to which woolen clothes keep the body warm in winter.
AIIMS-2002
Heat Transfer
149371
Two rods $A$ and $B$ of different materials are welded together as shown in figure. If their thermal conductivities are $K_{1}$ and $K_{2}$ the thermal conductivity of the composite rod will be-
D Given, Two rod each of length $d$ and same areas and thermal conductivities $K_{1}$ and $K_{2}$ are connected in parallel. Total heat $(\mathrm{H})=\mathrm{H}_{1}+\mathrm{H}_{2}$ $\frac{\mathrm{K}(2 \mathrm{~A})\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{K}_{1} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}+\frac{\mathrm{K}_{2} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}$ $\frac{2 \mathrm{KA}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}} \times\left[\mathrm{K}_{1}+\mathrm{K}_{2}\right]$ $\mathrm{K}=\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{2}$
149369
The two ends of a rod of length $L$ and a uniform cross sectional area $A$ are kept at two temperatures $T_{1}$ and $T_{2}\left(T_{1}>T_{2}\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$ through the rod in a steady state is given by:
C Rate of heat transfer through the rod of length $\mathrm{L}$ and uniform cross-sectional area $\mathrm{A}$ and temperatures $\mathrm{T}_{1}$ and $\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)$ in steady state. Here temperature difference $(\Delta \mathrm{T})=\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)$ The rate of heat transfer $(\mathrm{dQ} / \mathrm{dt})$ is given by: $\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\Delta \mathrm{T}}{\mathrm{R}}$ Since, $\quad \mathrm{R}=\frac{\rho \mathrm{L}}{\mathrm{A}}$ $\therefore \quad \frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{kA}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{L}} \quad\left(\because \mathrm{k}=\frac{1}{\rho}\right)$
AIIMS-26.05.2019(M) Shift-1
Heat Transfer
149370
Thermal conductivity of a material in CGS system is 0.4. In steady state, the rate of flow of heat is $10 \mathrm{cal} / \mathrm{s}-\mathrm{cm}^{2}$. The thermal gradient will be-
149362
Assertion: Two thin blankets put together are warmer than a single blanket of double the thickness. Reason: Thickness increases because of air layer enclosed between the two blankets.
1 If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
2 If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
3 If Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
Explanation:
C Two thin blankets put together are warmer than a single blanket of double the thickness because air is trapped in the space between two thin blankets. Since, air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.
AIIMS-2010
Heat Transfer
149364
Assertion: Woolen clothes keep the body warm in winter. Reason: Air is a bad conductor of heat.
1 If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
2 If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
3 If the Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
5 If the Assertion is incorrect but the Reason is correct.
Explanation:
A Woolen clothes keep the body warm in winter because air particle trapped inside the woolen clothes, As we know, air is bad conductor of heat due to which woolen clothes keep the body warm in winter.
AIIMS-2002
Heat Transfer
149371
Two rods $A$ and $B$ of different materials are welded together as shown in figure. If their thermal conductivities are $K_{1}$ and $K_{2}$ the thermal conductivity of the composite rod will be-
D Given, Two rod each of length $d$ and same areas and thermal conductivities $K_{1}$ and $K_{2}$ are connected in parallel. Total heat $(\mathrm{H})=\mathrm{H}_{1}+\mathrm{H}_{2}$ $\frac{\mathrm{K}(2 \mathrm{~A})\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{K}_{1} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}+\frac{\mathrm{K}_{2} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}$ $\frac{2 \mathrm{KA}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}} \times\left[\mathrm{K}_{1}+\mathrm{K}_{2}\right]$ $\mathrm{K}=\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{2}$
149369
The two ends of a rod of length $L$ and a uniform cross sectional area $A$ are kept at two temperatures $T_{1}$ and $T_{2}\left(T_{1}>T_{2}\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$ through the rod in a steady state is given by:
C Rate of heat transfer through the rod of length $\mathrm{L}$ and uniform cross-sectional area $\mathrm{A}$ and temperatures $\mathrm{T}_{1}$ and $\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)$ in steady state. Here temperature difference $(\Delta \mathrm{T})=\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)$ The rate of heat transfer $(\mathrm{dQ} / \mathrm{dt})$ is given by: $\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\Delta \mathrm{T}}{\mathrm{R}}$ Since, $\quad \mathrm{R}=\frac{\rho \mathrm{L}}{\mathrm{A}}$ $\therefore \quad \frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{kA}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{L}} \quad\left(\because \mathrm{k}=\frac{1}{\rho}\right)$
AIIMS-26.05.2019(M) Shift-1
Heat Transfer
149370
Thermal conductivity of a material in CGS system is 0.4. In steady state, the rate of flow of heat is $10 \mathrm{cal} / \mathrm{s}-\mathrm{cm}^{2}$. The thermal gradient will be-
149362
Assertion: Two thin blankets put together are warmer than a single blanket of double the thickness. Reason: Thickness increases because of air layer enclosed between the two blankets.
1 If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
2 If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
3 If Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
Explanation:
C Two thin blankets put together are warmer than a single blanket of double the thickness because air is trapped in the space between two thin blankets. Since, air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.
AIIMS-2010
Heat Transfer
149364
Assertion: Woolen clothes keep the body warm in winter. Reason: Air is a bad conductor of heat.
1 If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
2 If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
3 If the Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
5 If the Assertion is incorrect but the Reason is correct.
Explanation:
A Woolen clothes keep the body warm in winter because air particle trapped inside the woolen clothes, As we know, air is bad conductor of heat due to which woolen clothes keep the body warm in winter.
AIIMS-2002
Heat Transfer
149371
Two rods $A$ and $B$ of different materials are welded together as shown in figure. If their thermal conductivities are $K_{1}$ and $K_{2}$ the thermal conductivity of the composite rod will be-
D Given, Two rod each of length $d$ and same areas and thermal conductivities $K_{1}$ and $K_{2}$ are connected in parallel. Total heat $(\mathrm{H})=\mathrm{H}_{1}+\mathrm{H}_{2}$ $\frac{\mathrm{K}(2 \mathrm{~A})\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{K}_{1} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}+\frac{\mathrm{K}_{2} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}$ $\frac{2 \mathrm{KA}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}} \times\left[\mathrm{K}_{1}+\mathrm{K}_{2}\right]$ $\mathrm{K}=\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{2}$
149369
The two ends of a rod of length $L$ and a uniform cross sectional area $A$ are kept at two temperatures $T_{1}$ and $T_{2}\left(T_{1}>T_{2}\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$ through the rod in a steady state is given by:
C Rate of heat transfer through the rod of length $\mathrm{L}$ and uniform cross-sectional area $\mathrm{A}$ and temperatures $\mathrm{T}_{1}$ and $\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)$ in steady state. Here temperature difference $(\Delta \mathrm{T})=\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)$ The rate of heat transfer $(\mathrm{dQ} / \mathrm{dt})$ is given by: $\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\Delta \mathrm{T}}{\mathrm{R}}$ Since, $\quad \mathrm{R}=\frac{\rho \mathrm{L}}{\mathrm{A}}$ $\therefore \quad \frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{kA}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{L}} \quad\left(\because \mathrm{k}=\frac{1}{\rho}\right)$
AIIMS-26.05.2019(M) Shift-1
Heat Transfer
149370
Thermal conductivity of a material in CGS system is 0.4. In steady state, the rate of flow of heat is $10 \mathrm{cal} / \mathrm{s}-\mathrm{cm}^{2}$. The thermal gradient will be-
149362
Assertion: Two thin blankets put together are warmer than a single blanket of double the thickness. Reason: Thickness increases because of air layer enclosed between the two blankets.
1 If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
2 If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
3 If Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
Explanation:
C Two thin blankets put together are warmer than a single blanket of double the thickness because air is trapped in the space between two thin blankets. Since, air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.
AIIMS-2010
Heat Transfer
149364
Assertion: Woolen clothes keep the body warm in winter. Reason: Air is a bad conductor of heat.
1 If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
2 If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
3 If the Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
5 If the Assertion is incorrect but the Reason is correct.
Explanation:
A Woolen clothes keep the body warm in winter because air particle trapped inside the woolen clothes, As we know, air is bad conductor of heat due to which woolen clothes keep the body warm in winter.
AIIMS-2002
Heat Transfer
149371
Two rods $A$ and $B$ of different materials are welded together as shown in figure. If their thermal conductivities are $K_{1}$ and $K_{2}$ the thermal conductivity of the composite rod will be-
D Given, Two rod each of length $d$ and same areas and thermal conductivities $K_{1}$ and $K_{2}$ are connected in parallel. Total heat $(\mathrm{H})=\mathrm{H}_{1}+\mathrm{H}_{2}$ $\frac{\mathrm{K}(2 \mathrm{~A})\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{K}_{1} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}+\frac{\mathrm{K}_{2} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}$ $\frac{2 \mathrm{KA}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}} \times\left[\mathrm{K}_{1}+\mathrm{K}_{2}\right]$ $\mathrm{K}=\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{2}$
149369
The two ends of a rod of length $L$ and a uniform cross sectional area $A$ are kept at two temperatures $T_{1}$ and $T_{2}\left(T_{1}>T_{2}\right)$. The rate of heat transfer, $\frac{\mathrm{dQ}}{\mathrm{dt}}$ through the rod in a steady state is given by:
C Rate of heat transfer through the rod of length $\mathrm{L}$ and uniform cross-sectional area $\mathrm{A}$ and temperatures $\mathrm{T}_{1}$ and $\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)$ in steady state. Here temperature difference $(\Delta \mathrm{T})=\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)$ The rate of heat transfer $(\mathrm{dQ} / \mathrm{dt})$ is given by: $\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\Delta \mathrm{T}}{\mathrm{R}}$ Since, $\quad \mathrm{R}=\frac{\rho \mathrm{L}}{\mathrm{A}}$ $\therefore \quad \frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{kA}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{L}} \quad\left(\because \mathrm{k}=\frac{1}{\rho}\right)$
AIIMS-26.05.2019(M) Shift-1
Heat Transfer
149370
Thermal conductivity of a material in CGS system is 0.4. In steady state, the rate of flow of heat is $10 \mathrm{cal} / \mathrm{s}-\mathrm{cm}^{2}$. The thermal gradient will be-
149362
Assertion: Two thin blankets put together are warmer than a single blanket of double the thickness. Reason: Thickness increases because of air layer enclosed between the two blankets.
1 If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
2 If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
3 If Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
Explanation:
C Two thin blankets put together are warmer than a single blanket of double the thickness because air is trapped in the space between two thin blankets. Since, air is an insulator of heat, it prevents the escape of body heat. That is why two thin blankets are usually warmer than one thick blanket.
AIIMS-2010
Heat Transfer
149364
Assertion: Woolen clothes keep the body warm in winter. Reason: Air is a bad conductor of heat.
1 If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
2 If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
3 If the Assertion is correct but Reason is incorrect.
4 If both the Assertion and Reason are incorrect.
5 If the Assertion is incorrect but the Reason is correct.
Explanation:
A Woolen clothes keep the body warm in winter because air particle trapped inside the woolen clothes, As we know, air is bad conductor of heat due to which woolen clothes keep the body warm in winter.
AIIMS-2002
Heat Transfer
149371
Two rods $A$ and $B$ of different materials are welded together as shown in figure. If their thermal conductivities are $K_{1}$ and $K_{2}$ the thermal conductivity of the composite rod will be-
D Given, Two rod each of length $d$ and same areas and thermal conductivities $K_{1}$ and $K_{2}$ are connected in parallel. Total heat $(\mathrm{H})=\mathrm{H}_{1}+\mathrm{H}_{2}$ $\frac{\mathrm{K}(2 \mathrm{~A})\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{K}_{1} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}+\frac{\mathrm{K}_{2} \mathrm{~A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}$ $\frac{2 \mathrm{KA}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}}=\frac{\mathrm{A}\left(\theta_{1}-\theta_{2}\right)}{\mathrm{d}} \times\left[\mathrm{K}_{1}+\mathrm{K}_{2}\right]$ $\mathrm{K}=\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{2}$
