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JEE Main 2013 (9 Apr, Shift 1) · Wheatstone Bridge & Metre Bridge

Wheatstone Bridge & Metre Bridge question from JEE Main 2013 (9 Apr, Shift 1)

Q78JEE Main 2013 · 9 APR · SHIFT 1Easy

Wheatstone Bridge & Metre Bridge

In a metre bridge experiment null point is obtained at 40 cm from one end of the wire when resistance X is balanced against another resistance Y. If X < Y, then the new position of the null point from the same end, if one decides to balance a resistance of 3X against Y, will be close to:

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Answer: (c)

  1. First balance: XY=4060=23\frac{X}{Y} = \frac{40}{60} = \frac{2}{3}
  2. New: 3XY=2=l100−l\frac{3X}{Y} = 2 = \frac{l}{100 - l}
  3. l=200−2l⇒l=66.7 cm≈67 cml = 200 - 2l \Rightarrow l = 66.7\text{ cm} \approx 67\text{ cm}
  4. So the answer is (c) 67 cm.
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