The pitch of a screw gauge is `0.5mm` and there are 50 divisions on its circular scale and one main scale division `=0.5` mm. Before starting the measurement it is found that when jaws of the screw gauge are brought in contact, the zero of the circular scale lies 4 division above the reference line. when a metallic wire is placed between the jaws, five main scale divisions are clearly visible and `18^(th)` division on the circular scale coincides with the reference line. the diameter of the wire is

Options

A. `2.68mm`
B. `2.72mm`
C. `2.64mm`
D. `2.62mm`

Answer

C

Explanation

Zero error `=+4xx0.01=+0.04mm`
Measured diameter `=M.S.R+L.C.xxC.S.R`.
`=(5xx0.5)mm+(0.01mm)xx18=2.68,mm`
`:.` Actual diameter `=2.68-(0.04)=2.64mm`