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MHT CET202615 April 2026Evening ShiftPhysicsThermal Properties of MatterActual

The ratio of the thermal conductivity of two rods of different materials is 6:5. The two rods of same area of cross section and same thermal resistance will have the length in the ratio

Options

  1. A5 : 6
  2. B6 : 5
  3. C1 : 3
  4. D3 : 1

Correct answer

B. 6 : 5

Step-by-step solution

Thermal resistance of a rod is given by R = L KA Given that both rods have the same thermal resistance ( R₁ = R₂ ) and the same area of cross-section ( A₁ = A₂ = A ), we can write: L₁ K₁ A = L₂ K₂ A L₁ L₂ = K₁ K₂ The ratio of thermal conductivities is given as K₁ K₂ = 6 5 Therefore, L₁ L₂ = 6 5 The lengths of the rods are in the ratio 6 : 5 .

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