Q. Two rods of same length and material transfer a given amount of heat in 12 s, when they are joined end to end ($ie$, in series). But when they are joined in parallel, they will transfer same heat under same conditions in
A) 24 s
B) 3 s
C) 48 s
D) 1.5 s
Explanation
(b) $\mathrm{\Delta}t = \ \frac{\mathrm{\Delta}Q(\mathrm{\Delta}x)}{KA(\mathrm{\Delta}T)}$
When two rods of same length are joined in parallel,
$A\ \rightarrow 2\ and\ (\mathrm{\Delta}x) \rightarrow \frac{1}{2}\ times$
$\therefore\ \mathrm{\Delta}t\ becomes\frac{1}{4}\ times\ ie,\frac{1}{4} \times 12s = 3s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.