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 [image:11_image39.png]

Question

Dr. Abubacker · Accepted Answer

(a) $\frac{Q}{t} = \frac{KA\mathrm{\Delta}	heta}{l} \Rightarrow \frac{\mathrm{\Delta}	heta}{(l/KA)} = \frac{\mathrm{\Delta}	heta}{R}\ \lbrack R =$ Thermal resistance]
$\Rightarrow t \propto R\ \ \ \ \lbrack\because Q$ and $\mathrm{\Delta}	heta$ are same]
$\Rightarrow \frac{t_{p}}{t_{s}} = \frac{R_{P}}{R_{S}} = \frac{R/2}{2R} = \frac{1}{4} \Rightarrow t_{P} = \frac{t_{S}}{4} = \frac{4}{4} = 1min$
[Series resistance $R_{S} = R_{1} + R_{2}$ and parallel resistance $R_{P} = \frac{R_{1}R_{1}}{R_{2} + R_{2}}$]

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

Explanation

Reviewed by Dr. Abubacker

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