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10.2 , transmission of heat — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics10.2 , transmission of heat1 Mark
MCQ
Three identical rods have been joined at a junction to make it a $Y$ shape structure. If two free ends are maintained at $90\,^oC$ and the third end is at $30\,^oC$ , then what is the junction temperature $\theta $ ?......... $^oC$
  • A
    $40$
  • B
    $50$
  • C
    $60$
  • ✓
    $70$
✓

Answer

Correct option: D.
$70$
d
Themal resistance $=\frac{\mathrm{L}}{\mathrm{KA}}=$ same for all $=\mathrm{R}(\mathrm{let})$ using kirchoff's law for heat current

$\mathrm{i}_{1}+\mathrm{i}_{2}+\mathrm{i}_{3}=0$

$\Rightarrow \frac{30-\theta}{R}+\frac{90-\theta}{R}+\frac{90-\theta}{R}=0$

$30-\theta+180-2 \theta=0 \Rightarrow 210=3 \theta \Rightarrow \theta=70^{\circ} \mathrm{C}$

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