Q: The circular scale of a screw gauge has 200 divisions . When it is given 4 complete rotations , it moves through 2 mm . The least count of screw gauge is
(a) 0.25 x 10-2 cm
(b) 0.25 x 10-3 cm
(c) 0.001 cm
(d) 0.001 mm
Ans: (b)
Sol: $Pitch = \frac{2}{4} mm = 0.5 mm $
$\large L.C = \frac{Pitch}{200} = \frac{0.5}{200} mm $
Pitch = 0.25 x 10-2 mm
= 0.25 x 10-3 cm