Two identical square rods of metal are welded end to end as shown in figure (i) , 20 calories of heat flows through it in

Q: Two identical square rods of metal are welded end to end as shown in figure $(i)$ , $20$ calories of heat flows through it in $4$ minutes. If the rods are welded as shown in figure $(ii)$, the same amount of heat will flow through the rods in ....... $\min.$

a (a) $\frac{Q}{t} = \frac{{KA\,\Delta \theta }}{l}$$ = \frac{{\Delta \theta }}{{(l/KA)}} = \frac{{\Delta \theta }}{R}$ ( $R =$ Thermal resistance) ==> $t \propto R$ ( $Q$ and $\Delta \theta $ are same) ==> $\frac{{{t_P}}}{{{t_S}}} = \frac{{{R_P}}}{{{R_S}}} = \frac{{R/2}}{{2R}} = \frac{1}{4}$ ==>${t_P} = \frac{{{t_S}}}{4} = \frac{4}{4} = 1\min .$ (Series resistance ${R_S} = {R_1} + {R_2}$ and parallel resistance ${R_P} = \frac{{{R_1}{R_2}}}{{{R_1} + {R_2}}}$)

SECTION - A [PHYSICS - MCQ]

GSEB - English Medium

Two identical square rods of metal are welded end to end as shown in figure $(i)$ , $20$ calories of heat flows through it in $4$ minutes. If the rods are welded as shown in figure $(ii)$, the same amount of heat will flow through the rods in ....... $\min.$

A$1$
B$2$
C$4$
D$16$

Medium

STD 11 Science
NEET
STD 11 - 10.2. transmission of heat
Physics

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