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The diameter of a cylinder is measured using a Vernier Callipers with no zero error. It is found that the zero of the Vernier scale lies between 5.10 cm and 5.15 cm of the main scale. The Vernier scale has 50 divisions equivalent to 2.45 cm. The 24th division of the Vernier scale exactly coincides with one of the main scale divisions. The diameter of the cylinder is ...

My attempt
1 division of vernier scale is equivalent to 50/2.45 cm.
Least count of main scale = 0.05cm
Thus Vernier constant = 0.5-(50/2.45) cm

Surprisingly this is negative.?? I don't really know how to solve these kinds of problems. Please help me.

BMS
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Utkarsh
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1 Answers1

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When the zero lies between 5.10 and 5.15, it means that the diameter is more than 5.10 and less than 5.15. The length of the vernier scale is not important. Since the 24th mark (out of 50) lines up with another mark, then the additional amount is 24 parts of 0.05, since each mark is 0.05 (5.15 - 5.10) cm. The reading of the vernier is 5.124 cm. Google "reading a vernier" if you need more assistance.

LDC3
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  • But then what is the use of this statement "The Vernier scale has 50 divisions equivalent to 2.45 cm" – Utkarsh May 20 '14 at 04:32
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    Possibly to throw you off the right track. I don't know why it's there; it's not important to reading the vernier. – LDC3 May 20 '14 at 04:33
  • I guess you are correct because this was asked in a competitive exam and they intentionally add unnecessary info to throw students off the track. – Utkarsh May 20 '14 at 04:44