`1.56 × 10^5 J` of heat is conducted through is `2 m^2` wall of 12 cm thick in one hour. Temperature difference between the two sides of the wall is `20 ^@C.` The thermal conductivity of the material of the wall is (in `Wm ^(-1) K^(-1)`)

Options

A. 0.11
B. 0.13
C. 0.15
D. 1.2

Answer

B

Explanation

`(dQ)/( dt) = ( KA Delta T)/( x)`
`(1. 56 xx 10 ^(5))/( 3600) = ( K xx 2 xx 20)/( 12 xx 10 ^(-2))`
`implies K = (1. 56 xx 10 ^(5) xx12 xx 10 ^(-2))/( 3600 xx 2 xx 10) W m ^(-1) K^(-1) `
`implies K = 0.13 W m ^(-1) K ^(-1)`