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CUET · PHYSICS · PYQ PAPER 2023

Two resistances are connected in two gaps of a metre bridge. The balance point is 20 cm from the zero end. A resistance of \(3 \Omega\) is connected in series with the smaller resistance, then the null point shifts to 40 cm. The value of the smaller resistance is:

  1. A \(3 \Omega\)
  2. B \(6 \Omega\)
  3. C \(9 \Omega\)
  4. D \(12 \Omega\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(3 \Omega\)

Step-by-step Solution

Detailed explanation

\( \frac{R_1}{R_2} = \frac{20}{100-20} = \frac{1}{4} \) \( R_2 = 4R_1 \) \( \frac{R_1+3}{R_2} = \frac{40}{100-40} = \frac{2}{3} \) \( \frac{R_1+3}{4R_1} = \frac{2}{3} \) \( 3(R_1+3) = 8R_1 \) \( 3R_1+9 = 8R_1 \) \( 5R_1 = 9 \) \( R_1 = 1.8 \, \Omega \)
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