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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
There are two identical vessels filled with equal amounts of ice. The vessels are of different metals., If the ice melts in the two vessels in $20$ and $35$ minutes respectively, the ratio of the coefficients of thermal conductivity of the two metals is
  • A
    $4:7$
  • ✓
    $7:4$
  • C
    $16:49$
  • D
    $49:16$
✓

Answer

Correct option: B.
$7:4$
b
(b) $Q = \frac{{KA({\theta _1} - {\theta _2})}}{l}t = $ $ \Rightarrow {K_1}{t_1} = {K_2}{t_2}$ $ \Rightarrow \frac{{{K_1}}}{{{K_2}}} = \frac{{{t_2}}}{{{t_1}}} = \frac{{35}}{{20}} = \frac{7}{4}$
(As $Q$ , $l$ , $A$ and $({\theta _1} - {\theta _2})$ are same)

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