- 1(current)
Q. No.Two bodies \(A,B\) are maintained at temperatures \(\theta_A=100^\circ\text C\) and \(\theta_B=0^\circ\text C.\) Two thermally conducting rods \((P,~Q)\) of different conductivities and of different dimensions are connected between \(A\) and \(B.\) The conductivity of \(P\) is twice that of \(Q.\) The sides of the rods are insulated. If the mid-points of the two rods are connected to each other by a thin conducting wire (after equilibrium is reached),
| 1. | heat would flow from \(P\) to \(Q\). |
| 2. | heat would flow from \(Q\) to \(P\). |
| 3. | no flow of heat occurs between \(P\) & \(Q\). |
| 4. | flow of heat may occur back and forth between \(P\) & \(Q,\) varying with time. |
Subtopic: Â Conduction |
 51%
Level 3: 35%-60%
Hints
Two rods of the same length and the same area of the cross-section are joined. The temperature of the two ends is shown in the figure.
As we move along the rod, temperature varies as shown in the following figure.
Then:
1. \(K_{1}>K_{2}\)
2. \(K_{1}=K_{2}\)
3. \(K_{1}<K_{2}\)
4. none of these
Subtopic: Â Conduction |
 60%
Level 2: 60%+
Hints
Two metallic rods \((AB,CD)\) of identical dimensions are connected in parallel, their ends being maintained at the same two temperatures: ends \(A,C\rightarrow\) at \(T_1\) and ends \(B,D\rightarrow\) at \(T_2.\) The thermal conductivities of the rods are \(K_1~(\text{rod }AB)\) and \(K_2~(\text{rod }CD).\) If the two rods are replaced by a single rod of the same dimension (as any one of them), and the net thermal current remains unchanged, then the conductivity \(K\) of the new rod will be given by:
| 1. | \(K={\dfrac{K_1+K_2}{2}}\) | 2. | \(K=K_1+K_2\) |
| 3. | \({\dfrac{2}{K}}={\dfrac{1}{K_1}}+{\dfrac{1}{K_2}}\) | 4. | \({\dfrac{1}{K}}={\dfrac{1}{K_1}}+{\dfrac{1}{K_2}}\) |
Subtopic: Â Conduction |
Level 3: 35%-60%
Hints
- 1(current)
Q. No.
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