A metallic prong consists of 4 rods made of same material, cross-sections and same lengths as shown

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10-2.Transmission of Heat

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A metallic prong consists of $4$ rods made of the same material, cross-sections and same lengths as shown below. The three forked ends are kept at $100^{\circ} C$ and the handle end is at $0^{\circ} C$. The temperature of the junction is ............. $^{\circ} C$

A

$25$

B

$50$

C

$60$

D

$75$

(KVPY-2013)

Solution

(d)

Let junction temperature $=T^{\circ} C$.

As, heat inflow through three prongs = heat outflow through fourth prong.

So, $\quad 3 \frac{k A}{l}(100-T)=\frac{k A}{l}(T-0)$

$\Rightarrow 300-3 T =T$

$\text { or } T =75^{\circ} C$

Standard 11

Physics

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