1.

Three bars each of area of cross section A and length L are connected in series as shown in the figure. Thermal conductivities of their materials are K, 2K and 1.5K. If the temperatures of free end of first and the last bar are 200^(@)C and 18^(@)C. The value of theta_(1) and theta_(2) are (in steady state):

Answer»

`120^(@)C,80^(@)C`
`116^(@)C, 80^(@)C`
`116^(@)C, 74^(@)C`
`120^(@)C, 74^(@)C`

Solution :As we use `(DELTA Q)/(Delta t) =(KA(200 - theta_(1))/(2L)`
`rArr``(Delta Q)/(Deltat) =(2 K)(Atheta_(1) - theta_(2))/(2L)`
`rArr``(Delta Q)/(Delta t) =(1.5 K)A((theta_(2)-18))/(2L)`
or , `200 - theta_(1) = 2 theta_(1) - 2 theta_(2) = 1.5 theta_(2) - 27`
`theta_(1) = 116^(@)C, theta_(2) = 74^(@)C`


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