Question

Two full turns of the circular scale of a screw gauge cover a distance of `1mm` on its main scale. The total number of divisions on the circular scale is `50`. Further, it is found that the screw gauge has a zero error of `- 0.03mm`. While main scale reading of `3mm` and the number of circular scale divisions in line with the main scale as `35`. the dimeter of the wire is
A. `3.32mm`
B. `3.73 mm`
C. `3.67mm`
D. 3.38mm`

Answer 1

Least count of screw gague
`=(0.5)/(50) mm = 0.01 mm`
`:.` Reading =[Main scale reading + circular scale reading `xx L.C` -(zero error)
`=[3+35 xx 0.01] - (-0.03) = 3.38 MM` .