In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 50 divisions on the circular scale, and the main scale moves by 0.5 mm on a complete rotation. For a particular observation the reading on the main scale is 5 mm and the 20 text th division of the circular scale coincides with reference line. Calculate the true reading.

Question

In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 50 divisions on the circular scale, and the main scale moves by 0.5 mm on a complete rotation. For a particular observation the reading on the main scale is 5 mm and the 20 text th division of the circular scale coincides with reference line. Calculate the true reading. (A) 5.00 mm (B) 5.25 mm (C) 5.15 mm (D) 5.20 mm

Tardigrade Admin · Accepted Answer

Least count (L.C) =(0.5/50) True reading =5+(0.5/50) × 20-(0.5/50) × 5 =5+(0.5/50)(15)=5.15 mm

5.00 mm

5.25 mm

5.15 mm

5.20 mm

Least count (L.C) =500.5​ True reading =5+500.5​×20−500.5​×5 =5+500.5​(15)=5.15mm

Least count (L.C) $= \frac{0.5}{50}$
True reading $= 5 + \frac{0.5}{50} \times 20 - \frac{0.5}{50} \times 5$
$= 5 + \frac{0.5}{50} (15) = 5.15 mm$