Question

A slab consists of two parallel layers of copper and brass of the same thickness and having thermal conductivities in the ratio 1 : 4. If the free face of brass is at and that of copper at , the temperature of interface is

• A. 80°C
• B. 20°C
• C. 60°C
• D. 40°C

Answer 1

Answer: (A)

80°C

Answer 2

Temperature of interface

θ = $\frac { K _ { 1 } \theta _ { 1 } + K _ { 2 } \theta _ { 2 } } { K _ { 1 } + K _ { 2 } }$

$\left( \because \frac { K _ { 1 } } { K _ { 2 } } = \frac { 1 } { 4 } \Rightarrow \right.$If K₁ = K then K₂ = 4K)

⇒ $\theta = \frac { K \times 0 + 4 K \times 100 } { 5 K }$= 80°C