JEE Main20206 Sep 2020Evening ShiftPhysicsThermal Properties of MatterActual
Three rods of identical cross-section and length are made of three different materials of thermal conductivity K 1 , K 2 and K 3 , respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at 100 ° C and the other at 0 ° C (see figure). If the joints of the rod are at 70 ° C and 20 ° C in steady and there is no loss of energy from t
Options
- AK 1 : K 3 = 2 : 3 , K 2 : K 3 = 2 : 5
- BK 1 < K 2 < K 3
- CK 1 : K 2 = 5 : 2 , K 1 : K 3 = 3 : 5
- DK 1 > K 2 > K 3
Correct answer
A. K 1 : K 3 = 2 : 3 , K 2 : K 3 = 2 : 5
Step-by-step solution
K 1 ( 100 - 70 ) = K 2 ( 70 - 20 ) = K 3 ( 20 - 0 ) K 1 30 = K 2 ( 50 ) = K 3 ( 20 ) ⇒ K 1 : K 2 : K 3 = 10 : 6 : 15 K 1 : K 3 = 2 : 3