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JEE Main202431 Jan 2024Evening ShiftPhysicsCurrent ElectricityActual

The resistance per centimeter of a meter bridge wire is r , with X Ω resistance in left gap. Balancing length from left end is at 40 cm with 25 Ω resistance in right gap. Now the wire is replaced by another wire of 2 r resistance per centimeter. The new balancing length for same settings will be at

Options

  1. A20 cm
  2. B10 cm
  3. C80 cm
  4. D40 cm

Correct answer

D. 40 cm

Step-by-step solution

For first case: X r l 1 = 25 r l 2 ... (i) For second case: X 2 r l ' 1 = 25 2 r l ' 2 ... (ii) From (i) and (ii), we get l ' 1 l 1 = l ' 2 l 2 also total length is constant. Therefore, balance length doesn't change and l ' 1 = l 1 = 40 cm

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