Q: While measuring diameter of a wire using a screw gauge , the main scale reading is 7 mm and zero of circular scale is 35 division above the reference line . If screw gauge has a zero error of -0.003 cm , the correct diameter of wire is (given Least count = 0.001 cm)
(a) 0.735 cm
(b) 0.732 cm
(c) 0.738 cm
(d) 7.38 cm
Ans: (c)
Sol: Observed diameter = 0.7 cm + 35 x 0.001 cm
= 0.735 cm
Corrected diameter = (0.735 + 0.003) cm = 0.738 cm