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:  Conduction |
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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:  Conduction |
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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:  Conduction |
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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. 3(K1+K2)2

2. K1+K2

3. 2(K1+K2)

4. K1+K22

Subtopic:  Conduction |
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From NCERT
NEET - 2017
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