Wires A and B have identical lengths and have circular cross-sections. radius of A is twice radius o

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10-2.Transmission of Heat

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Wires $A$ and $B$ have identical lengths and have circular cross-sections. The radius of $A$ is twice the radius of $B$ $i.e.$ ${r_A} = 2{r_B}$. For a given temperature difference between the two ends, both wires conduct heat at the same rate. The relation between the thermal conductivities is given by

${K_A} = 4{K_B}$

${K_A} = 2{K_B}$

${K_A} = {K_B}/2$

${K_A} = {K_B}/4$

Solution

(d) $\frac{Q}{t} = \frac{{KA\Delta \theta }}{l} \Rightarrow \frac{{{K_A}}}{{{K_B}}} = \frac{{{A_B}}}{{{A_A}}} = {\left( {\frac{{{r_B}}}{{{r_B}}}} \right)^2} = \frac{1}{4} \Rightarrow {K_A} = \frac{{{K_B}}}{4}$

Standard 11

Physics

Two different rods $A$ and $B$ are kept as shown in figure. The ratio of thermal conductivities of $A$ and $B$ is

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Two identical square rods of metal are welded end to end as shown in figure $(a)$. Assume that $10\, cal$ of heat flows through the rods in $2\, min$. Now the rods are welded as shown in figure, $(b)$. The time it would take for $10$ cal to flow through the rods now, is …….. $\min$

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Two rods one made of copper and other made of steel of the same length and same cross sectional area are joined together. The thermal conductivity of copper and steel are $385\,J\,s ^{-1}\,K ^{-1}\,m ^{-1}$ and $50\,J\,s ^{-1}\,K ^{-1}\,m ^{-1}$ respectively. The free ends of copper and steel are held at $100^{\circ}\,C$ and $0^{\circ}\,C$ respectively. The temperature at the junction is, nearly $…….^{\circ}\,C$

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(NEET-2022)

In variable state, the rate of flow of heat is controlled by

easy

The thermal conductivity of a material in $CGS$ system is $0.4$ . In steady state, the rate of flow of heat $10 cal/sec-cm2$ , then the thermal gradient will be ……. $^oC/cm$

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Solution

Similar Questions

Two different rods $A$ and $B$ are kept as shown in figure. The ratio of thermal conductivities of $A$ and $B$ is

Two identical square rods of metal are welded end to end as shown in figure $(a)$. Assume that $10\, cal$ of heat flows through the rods in $2\, min$. Now the rods are welded as shown in figure, $(b)$. The time it would take for $10$ cal to flow through the rods now, is …….. $\min$

In variable state, the rate of flow of heat is controlled by

The thermal conductivity of a material in $CGS$ system is $0.4$ . In steady state, the rate of flow of heat $10 cal/sec-cm2$ , then the thermal gradient will be ……. $^oC/cm$

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