A screw gauge with a pitch of 1 mm has 100 divisions on its circular scale. What it is used to measure the diameter of a thin wire, the main scale reading is 3 mm and the circular scale reading is 45. If D is the diameter of the wire in mm, then find the value of D.

Answer

3.45

Explanation

Least count `= ("Pitch ")/( "No. of division ") = (1 mm)/(100) = 0.01 mm `
Diameter of wire main scale + circular scale reading
= 3 mm+ (L. C) `xx` No. of division
= 3 mm + 0.01 `xx` 45
D = 3.45 mm