Q135 / 150 · MHT CET 2023 (09 May Shift 1) · Physics

In a meter bridge experiment null point is obtained at $l \mathrm{~cm}$ from the left end. If the meter bridge wire is replaced by a wire of same material but twice the area of across-section, then the null point is obtained at a distance

  • A
    $2 l \mathrm{~cm}$ from left end.
  • Correct answer
    B
    $l \mathrm{~cm}$ from left end.
  • C
    $l / 2 \mathrm{~cm}$ from left end.
  • D
    $l / 4 \mathrm{~cm}$ from left end.

Solution

At null condition, $\frac{\mathrm{R}_1}{\mathrm{R}_2}=\frac{\mathrm{X}}{100-\mathrm{X}}$ This condition is independent of the crosssectional area of the wire used. $\therefore \quad$ The null point will remain the same. (i.e., $l \mathrm{~cm}$ from left end)

Hence, the correct answer is option: 'B'.

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