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AP EAMCET · PHYSICS · Thermal Properties of Matter

A rectangular slab consists of two cubes of copper and brass of equal sides having thermal conductivities in the ratio \(4: 1\). If the free face of brass is at \(0{ }^{\circ} \mathrm{C}\) and that of copper is at \(100^{\circ} \mathrm{C}\), then the temperature of their interface is

  1. A \(80^{\circ} \mathrm{C}\)
  2. B \(20^{\circ} \mathrm{C}\)
  3. C \(60^{\circ} \mathrm{C}\)
  4. D \(40^{\circ} \mathrm{C}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(80^{\circ} \mathrm{C}\)

Step-by-step Solution

Detailed explanation

\( \frac{K_{Cu} A (T_{Cu} - T_i)}{L} = \frac{K_{Br} A (T_i - T_{Br})}{L} \) \( K_{Cu} (T_{Cu} - T_i) = K_{Br} (T_i - T_{Br}) \) \( 4K (100 - T_i) = K (T_i - 0) \) \( 400 - 4T_i = T_i \) \( 5T_i = 400 \) \( T_i = 80^{\circ} \mathrm{C} \)