Three rods of identical dimensions but made of materials of conductivities $$K,~2K,~K$$ are connected in series. The two ends $$A~,B$$ are maintained at temperatures of $$0~^{\circ} \text{C},~100~^{\circ} \text{C}$$ respectively. Assume no loss of heat from the sides. The temperatures of the junctions $$X,~Y$$ are:

1. $$25~^\circ\text C,~75~^\circ\text C$$
2. $$40~^\circ\text C,~60~^\circ\text C$$
3. $$20~^\circ\text C,~80~^\circ\text C$$
4. $$30~^\circ\text C,~70~^\circ\text C$$
Subtopic: Â Conduction |
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From NCERT
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If the ends of the meter stick are maintained at $$\theta_1$$$$^\circ \text{C}$$ and $$\theta_2$$$$^\circ \text{C},$$ the temperatures measured at the $$25$$ cm and $$80$$ cm marks are observed to be $$35^\circ \text{C}$$ and $$68^\circ \text{C}$$ respectively. Then the temperatures of the left end ($$\theta_1$$$$^\circ \text{C}$$) and the right end ($$\theta_2$$$$^\circ \text{C}$$) are:
 1 $$\theta_{1}=0, ~\theta_{2}=90$$ 2 $$\theta_{1}=10,~\theta_{2}=85$$ 3 $$\theta_{1}=20, ~\theta_{2}=80$$ 4 $$\theta_{1}=30, ~\theta_{2}=100$$
Subtopic: Â Conduction |
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From NCERT
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Two rods of identical dimensions are joined end-to-end, and the ends of the composite rod are kept at $$0^\circ\mathrm{ C}$$ and $$100^\circ\mathrm{ C}$$ (as shown in the diagram). The temperature of the joint is found to be $$40^\circ\mathrm{ C}.$$ Assuming no loss of heat through the sides of the rods, the ratio of the conductivities of the rods $$K_1/K_2$$ is:

1. $$\frac32$$
2. $$\frac23$$
3. $$\frac11$$
4. $$\frac{\sqrt3}{\sqrt2}$$

Subtopic: Â Conduction |
Â 78%
From NCERT
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Two rods $$A$$ and $$B$$ of different materials are welded together as shown in the figure. Their thermal conductivities are $$K_1$$ and $$K_2.$$ The thermal conductivity of the composite rod will be:

 1 $$\frac{3(K_1+K_2)}{2}$$ 2 $$K_1+K_2$$ 3 $$2(K_1+K_2)$$ 4 $$\frac{(K_1+K_2)}{2}$$
Subtopic: Â Conduction |
Â 72%
From NCERT
NEET - 2017
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