Three rods made of same material and having the same cross-section have been joined as shown in fig. each rod is of the same length. The left and the right ends are kept at `0^(@)C` and `90^(@)C` respectively. What will be the temperature of the junction of the three rods?

Explanation

Let R be the thermal resistance of each rod and `theta^(@)C` be the temperature of the junction B as shown in fig. then
Heat current in CB + heat current in FB = heat current in BA
or `(90-theta)/(R_H) +(90-theta)/(R_H) = (theta-0)/(R_H)`
`[ :' "Heat current" = (Delta Q)/(Delta t)=(Delta T)/(R_H)]`
or `180 - 2 theta = theta or theta = 60^(@)`.