Question

Fig shows two co–axial cylinder of same length radii R and 2R. The thermal conductivity of inner and outer cylinder is K and K₁ respectively. The equivalent thermal conductivity of the arrangment is 1.5 K. Then K₁ is

(a) 2K/3

(b) 3K/3

(c) 3K/5

(d) 5K/3

Answer 1

(d) 5K/3

Let θ₁ and θ₂ be the temperature of the two ends of the arrangement. Then the rate of flow of heat is