Q: When screw gauge is completely closed , zero of circular scale is 4 divisions below the reference line of graduation . If least count of screw gauge is 0.001 cm , the zero correction is
(a) -0.004 cm
(b) +0.004 cm
(c) -0.004 mm
(d) +0.004 mm
Sol: As zero of circular scale is below the reference line of graduation , zero correction is negative .
Its magnitude is 4 × 0.001 cm = 0.004 cm
Ans : (a)