`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

Rate of heat flow through the wall is
`(Delta Q)/(Delta t) = (KA Delta T)/(t)`
Substituting the given values, we get
`(1.56 xx 10^(5)J)/(3600s) = (K xx 2m^(2) xx 20^(@)C)/(12 xx 10^(-2)m)`
`K = (1.56 xx 10^(5) xx 12 xx 10^(-2))/(3600 xx 2 xx 20) W m^(-1) K^(-1)`
or `K= (1.56)/(12) W m^(-1) K^(-1) = 0.13 W m^(-1) K^(-1)`