Q.

While measuring diameter of wire using screw gauge the following readings were noted. Main scale reading is 1 mm and circular scale reading is equal to 42 divisions. Pitch of screw gauge is 1 mm and it has 100 divisions on circular scale. The diameter of the wire is x50 mm. The value of x is            [2024]

1 142  
2 21  
3 42  
4 71  

Ans.

(4)         

              MSR = 1 mm, CSR = 42, pitch = 1 mm

               LC=pitchNo. of CSD=(1100)=0.01mm

               Reading by screw gauge = Main scale reading + Least count × circular scale reading

                Diameter = MSR + LC × CSD = 1 mm + 0.1 mm × 42 = 1.42 mm

                Diameter = 1.42 mm = x50x=71