The main scale of a vernier callipers is calibrated in mm and 19 divisions of main scale are equal in length to 20 divisions of vernier scale. In measuring the diameter of a cylinder by this instrument, the main scale reads 35 divisions and 4th division of vernier scale coinsides with a main scale division.Find:
(ii)Radius of cylinder.
Value of 1 m.s.d = 1 mm = 0.1 cm
20 vernier divisions = 19 main scale divisions
Least count = 0.005 cm
Main scale reading = 35 mm = 3.5 cm
Since 4th division of the main scale coincides with the main scale, i.e. p = 4.
Therefore, the vernier scale reading = 4 × 0.005 cm = 0.02 cm
Total reading = Main scale reading + vernier scale reading
= (3.5 + 0.02) cm
= 3.52 cm
= (3.52/2) cm
= 1.76 cm
Radius of the cylinder = 1.76 cm