A screw gauge has 50 divisions on its circular scale. The circular scale is 4 units ahead of the pitch scale marking , prior to use. Upon one complete rotation of the circular scale, a displacement of 0.5 mm is noticed on the pitch scale . The nature of zero error involved , and the least count of the screw gauge, are respectively.

Options

A. Negative, `2 mum`
B. Positive, `10 mum`
C. Positive, 0.1 mm
D. Positive, `0.1 mum`

Answer

B

Explanation

Least count of screw gauge `= ("Pitch")/("Number of division on circular scale")`
`= (0.5)/50 mm=1xx10^(-5)m = 10 mum`
Zero error in positive.