Q.

In a Vernier calliper, when both jaws touch each other, zero or the Vernier scale shifts towards left and its 4th division coincides exactly with a certain division on main scale. If 50 Vernier scale divisions are equal to 49 main scale divisions and zero error in the instrument is 0.4 mm, then how many main scale divisions are there in 1 cm             [2024]

1 5  
2 20  
3 10  
4 40  

Ans.

(2)         

                50 VSD=49 MSD1 VSD=4950 MSD

                 LC=1 MSD-1 VSD=1 MSD-4950 MSD=MSD50

                 Now,|zero error|=|0-4(L.C)|

                 0.04=|-4(L.C)|L.C.= 0.01mm

                  Using (i) and (ii), MSD50=0.01

                   MSD=0.5mmMSD=1cmN

                 N=1cm0.5mm=100mm5mm=20