JEE Main & Advanced
Physics
Transmission of Heat
Question Bank
Conduction
question_answer
Two rods of same length and material transfer a given amount of heat in 12 seconds, when they are joined end to end. But when they are joined lengthwise, then they will transfer same heat in same conditions in [BHU 1998; UPSEAT 2002]
A) 24 s
B) 3 s
C) 1.5 s
D) 48s
Correct Answer:
D
Solution :
Let the heat transferred be Q. When rods are joined end to end. Heat transferred by each rod\[=Q=\frac{KA\Delta \theta }{l}\times 12\] ?..(i) When rods are joined lengthwise, \[Q=\frac{KA\Delta \theta }{2l}t\] ?..(ii) From equation (i) and (ii) we get \[t=48\ s\]