A rod `CD` of thermal resistance `5.0KW_(-1)` is joined at the middle of an identical rod `AB` as shown in figure. The ends `A`,` B` and `D` are maintained at `100^(@)C` , `0^(@)C` and `25^(@)C` respectively. Find the heat current in `CD`.

Answer

`4.0 W`

Explanation

(Thermal resistance) `R = (L)/(KA) = 5.0 K//W`
`rArr`
`(T_(A)-T_(C))/(R//2) +(T_(D)-T_(C))/(R ) +(T_(B)-T_(C))/(R//2) = 0`
`2T_(A) - 2T_(C) +T_(D) - T_(C) +2T_(B) -2T_(C) = 0`
`200 +25 +0 = 5T_(C) T_(C) =(225)/(5) = 45`
`i_(CD) =(T_(C)-T_(D))/(R ) = (45 -25)/(5) = 4W`