Q: The vernier constant of a vernier callipers is 0.1 mm and it has zero error of 0.04 cm . While measuring diameter of a rod , the main scale reading is 1.2 cm and 5th vernier division is coinciding with any scale division . The corrected diameter of the rod is

(a) 1.21 cm

(b) 1.21 mm

(c) 1.29 mm

(d) 1.29 cm

Sol: V.C = 0.1 mm = 0.01 cm ; zero error = 0.04 cm

Zero correction = -0.04 cm

Observed diameter = (1.2 + 5 × 0.01) cm = 1.25 cm

Corrected diameter = (1.25 – 0.04) cm = 1.21 cm