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JEE Main 2008 (AIEEE) · Least Count, Vernier Callipers & Screw Gauge

Least Count, Vernier Callipers & Screw Gauge question from JEE Main 2008 (AIEEE)

Q66JEE Main 2008 · AIEEEDifficult

Least Count, Vernier Callipers & Screw Gauge

Two full turns of the circular scale of a screw gauge cover a distance of 1 mm on its main scale. The total number of divisions on the circular scale is 50. Further, it is found that the screw gauge has a zero error of − 0.03 mm. While measuring the diameter of a thin wire, a student notes the main scale reading of 3 mm and the number of circular scale divisions in line with the main scale as 35. The diameter of the wire is

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Answer: (d)

  1. Pitch =12=0.5 mm= \dfrac{1}{2} = 0.5\text{ mm}; LC =0.550=0.01 mm= \dfrac{0.5}{50} = 0.01\text{ mm}
  2. Observed reading =3+35×0.01=3.35 mm= 3 + 35\times 0.01 = 3.35\text{ mm}
  3. Diameter =3.35−(−0.03)=3.38 mm= 3.35 - (-0.03) = 3.38\text{ mm}. So the answer is (d).
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