Two insulated metal bars each of length 5 cm and rectangular cross section with sides 2 cm and 3 cm are wedged between two walls, one held at `100^@C` and the other at `0^@C`. The bars are made of lead and silver. `K_(pb)=350 W//mK,K_(Ag)=425 W//mK`.
Equevalent thermal resistence of the two bar system is

Options

A. `0.1(K)/(W)`
B. `0.23(K)/(W)`
C. `0.19(W)/(W)`
D. `0.42(K)/(W)`

Answer

A

Explanation

`(1)/(R_(eq))=(1)/(R_(pb))+(1)/(R_(Ag))=(21)/(5)+(51)/(10)`
`=(42+51)/(10)=(93)/(10)`
`R_(eq)=(10)/(93)=0.107Wcong0.1(K)/(W)`