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NEET 2012 (AIPMT, Prelims) · Combination of Resistors

Combination of Resistors question from NEET 2012 (AIPMT, Prelims)

Q72NEET 2012 · AIPMT · PRELIMSMedium

Combination of Resistors

A ring is made of a wire having a resistance R0 = 12 Ω\Omega. Find the points A and B, as shown in the figure, at which a current carrying conductor should be connected so that the resistance R of the sub circuit between these point is equal to 83Ω\frac{8}{3}\Omega.

Figure

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Answer: (d)

  1. Let the arcs be R1R_1 and R2R_2: R1+R2=12R_1 + R_2 = 12 and R1R212=83\dfrac{R_1 R_2}{12} = \dfrac{8}{3}, so R1R2=32R_1R_2 = 32.
  2. Solving: R1=4 ΩR_1 = 4\ \Omega, R2=8 ΩR_2 = 8\ \Omega.
  3. R∝lR \propto l, so l1l2=48=12\dfrac{l_1}{l_2} = \dfrac{4}{8} = \dfrac{1}{2}
  4. So the answer is (d).
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