The ratio of thermal conductivities of two rods is `5:3`. If the thermal resistances of the two rods of same, lengths of the rod is :

Options

A. `5/3`
B. `3/5`
C. `2/3`
D. `9/4`

Answer

A

Explanation

Thermal resistance `R=l/(kA)`
Here `R_(1)=R_(2)" "rArr" "(l_(1))/(k_(1)A_(1))=(l_(2))/(k_(1)A_(2))`.
As thickness is same `A_(1)=A_(2)`.
`:.(l_(1))/(l_(2))=(k_(1))/(k_(2))=5//3`
Thus correct choice is (a).