Two identical plates of metal are welded end to end as shown in figure (A). 20 cal of heat flows through it in 4 minutes when the ends were maintained at different temperatures. If the plates are welded as shown in figure (B) and the ends were maintained at same temperature as in first case, the same amount of heat will flow through the plates in how many minutes?

Question

Two identical plates of metal are welded end to end as shown in figure (A). 20 cal of heat flows through it in 4 minutes when the ends were maintained at different temperatures. If the plates are welded as shown in figure (B) and the ends were maintained at same temperature as in first case, the same amount of heat will flow through the plates in how many minutes? (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

(20/4)=(d Q/d t)=(k A/2 L)(Δ T) ; (20/t)=(k × 2 A/L) Δ T ⇒ T=1 min

420​=dtdQ​=2LkA​(ΔT);t20​=Lk×2A​ΔT ⇒T=1min

$\frac{20}{4} = \frac{d Q}{d t} = \frac{k A}{2 L} (Δ T); \frac{20}{t} = \frac{k \times 2 A}{L} Δ T$
$\Rightarrow T = 1 min$