Question

A slab consist 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 100°C and that of copper at 0°C, the temperature of interface is ______.

विकल्प

• 80°C

• 20°C

• 60°C

• 40°C

Answer 1

A slab consist 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 100°C and that of copper at 0°C, the temperature of interface is 80°C.

Explanation:

100 – T°C = `"R"_"B"/("R"_"B"+"R"_"C")xx[100-0]`

⇒ T = 100 `["R"_"C"/("R"_"B"+"R"_"C")]`

We know that R = `1/"KA"` 

T = `(1/"K"_"C")/(1/"K"_"B"+1/"K"_"C")`100

= `1/("K"_"C"/"K"_"B"+1)xx100`    `("Where"  "K"_"C"/"K"_"B"=1/4)`

= `4/5xx100`

= 80°C