Three rods of material 'x' and three rods of materialy are connected as shown in All the rods are of identical length and cross section If the end `A` is maintained at `60^(@)C` and the junction `E` at `10^(@0C` find effective Thermal Resistance Given length of each rod =1 area of cross-section =A conductivity of x=K and conductivity of `y =2K`
.

Options

A. `(4l)/(3KA)`
B. `(7l)/(6KA)`
C. `(4KA)/(3l)`
D. `(7KA)/(3l)`

Answer

B

Explanation

No heat is flowing through the road `CD`
`R_(eq)=R_(AB)+R_(BE),R_(BE) =(2RxxR)/(2R+R)=(2R)/(3)`
`R_(eq) = (R )/(2)+(2R)/(3)=(7R)/(6) =(7l)/(6KA)`
.