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JEE Main 2018 (15 Apr, Shift 1) · Least Count, Vernier Callipers & Screw Gauge

Least Count, Vernier Callipers & Screw Gauge question from JEE Main 2018 (15 Apr, Shift 1)

Q58JEE Main 2018 · 15 APR · SHIFT 1Medium

Least Count, Vernier Callipers & Screw Gauge

In a screw gauge, 55 complete rotations of the screw cause it to move a linear distance of 0.25 cm0.25\text{ cm} There are 100100 circular scale divisions. The thickness of a wire measured by this screw gauge gives a reading of 44 main scale divisions and 3030 circular scale divisions. Assuming negligible zero error, the thickness of the wire is:

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Answer: (b)

  1. Pitch =0.255=0.05 cm= \dfrac{0.25}{5} = 0.05\text{ cm} (one main scale division)
  2. LC =0.05100=0.0005 cm= \dfrac{0.05}{100} = 0.0005\text{ cm}
  3. Thickness =4×0.05+30×0.0005=0.2+0.015=0.2150 cm= 4\times 0.05 + 30\times 0.0005 = 0.2 + 0.015 = 0.2150\text{ cm}
  4. So the answer is (b).
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