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NEET 2013
Exam
NEET
Year
2013
Subject
Physics
Chapter
Thermal Properties of Matter

NEET 2013 · Physics · Thermal Properties of Matter

Two metal rods 1 and 2 of same lengths have same temperature...

Two metal rods 1 and 2 of same lengths have same temperature difference between their ends. Their thermal conductivities are K1K_1 and K2K_2 and crosssectional areas A1A_1 and A2A_2 respectively. If the rate of heat conduction in 1 is four times that in 2 , then:

Options

  1. AK1A1=4K2A2K_1 A_1=4 K_2 A_2
  2. BK1A1=2K2A2K_1 A_1=2 K_2 A_2
  3. C4K1A1=K2A24 K_1 A_1=K_2 A_2
  4. DK1A1=K2A2K_1 A_1=K_2 A_2

Correct answer

A. K1A1=4K2A2K_1 A_1=4 K_2 A_2

Step-by-step solution

Let L=L= length of each rod Temperature difference =ΔT∴=\Delta T\therefore Rate of flow of rod (i) is H1=K1A1ΔTLandRateofflowofrod(2)isH_1=\frac{K_1 A_1 \Delta T}{L} and Rate of flow of rod (2) isH_2=\frac{K_2 A_2 \Delta T}{L}fromtheequationfrom the equationH1=4H2⇒K1A1ΔTL=4K2A2ΔTL⇒K1A1=4K2A2\begin{array}{rlrl}H_1 & =4 H_2 \\ \Rightarrow & \frac{K_1 A_1 \Delta \mathrm{T}}{L}& =4 \frac{K_2 A_2 \Delta T}{L}\\ \Rightarrow & K_1 A_1 & =4 K_2 A_2 \end{array}$
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