A screw gauge of pitch 0 . 5 mm is used to measure the diameter of uniform wire of length 6 . 8 cm , the main scale reading is 1 . 5 mm and circular scale reading is 7 . The calculated curved surface area of wire to appropriate significant figures is [Screw gauge has 50 divisions on the circular scale]

Step-by-step solution

Least Count (L.C) = P N = 0 . 5   mm 50 = 0 . 01   mm Length of wire = 6 . 8   cm Diameter of wire = 1 . 5   mm + 7 × L.C = 1 . 5   mm + 7 × . 01 = 1 . 57   mm Curved surface area = π D l = 3 . 14 × 6 . 8 × 1 . 57 × 10 - 1   cm 2 = 3 . 352   cm 2 = 3 . 4   cm 2