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JEE Advanced2007PhysicsCurrent ElectricityActual

A resistance of 2 is connected across one gap of a meter-bridge (the length of the wire is 100 ~cm ) and an unknown resistance, greater than 2 , is connected across the other gap. When these resistances are interchanged, the balance point shifts by 20 ~cm . Neglecting any corrections, the unknown resistance is

Options

  1. A3
  2. B4
  3. C5
  4. D6

Correct answer

A. 3

Step-by-step solution

aligned & R & >2 & 100-x & >x Applying & P Q & = R S aligned We have aligned & 2 R = x 100-x & R 2 = x+20 80-x aligned Solving Eqs. (i) and (ii), we get R=3 Answer is (a).

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