Source: Extra Practice
The pitch of a screw gauge is 1 mm and there are 100 divisions on the circular scale. While measuring the diameter of a wire, the linear scale reads 1 mm and 47th division on the circular scale coincides with the reference line. The diameter is:
Options
Option A is correct
1.47 mm
Option B
1.047 mm
Option C
1.0047 mm
Option D
1.47 cm
Explanation
Least Count (LC) = Pitch / No. of divisions = 1 mm / 100 = 0.01 mm. Diameter = Main Scale Reading + (Circular Scale Reading × LC) = 1 mm + (47 × 0.01 mm) = 1 + 0.47 = 1.47 mm. 1.047 mm and 1.0047 mm are errors in LC calculation. 1.47 cm uses incorrect units.