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Properties of Matter question

2001 · Q161
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Properties of Matter question

2001 · Q161

NEETPhysicsProperties of MatterMCQ+4 / −1
A cylindrical rod having temperature T1 and T2 at its end. The rate of flow of heat Q1 cal/sec. If all the linear dimension are doubled keeping temperature constant, then rate of flow of heat Q2 will be
  1. A
    4Q1
  2. B
    2Q1
  3. C
    Q14{{{Q_1}} \over 4}4Q1​​
  4. D
    Q12{{{Q_1}} \over 2}2Q1​​
View written solutionFree

Correct answer: B

Heat flow rate dQdt=KA(T1−T2)L=Q{{dQ} \over {dt}} = {{KA\left( {{T_1} - {T_2}} \right)} \over L} = QdtdQ​=LKA(T1​−T2​)​=Q

When linear dimensions are double.

A1∝r12,L1=L{A_1} \propto r_1^2,{L_1} = LA1​∝r12​,L1​=L

A2∝4r12,L2=2L⇒Q2=2Q1{A_2} \propto 4r_1^2,{L_2} = 2L \Rightarrow {Q_2} = 2{Q_1}A2​∝4r12​,L2​=2L⇒Q2​=2Q1​

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