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 mm. The value of is [2024]
142
21
42
71
(D) MSR = 1 mm, CSR = 42, pitch = 1 mm
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 =
There are 100 divisions on the circular scale of a screw gauge of pitch 1 mm. With no measuring quantity in between the jaws, the zero of the circular scale lies 5 divisions below the reference line. The diameter of a wire is then measured using this screw gauge. It is found that 4 linear scale divisions are clearly visible while 60 divisions on circular scale coincide with the reference line. The diameter of the wire is [2024]
4.60 mm
3.35 mm
4.65 mm
4.55 mm
(D) Pitch P = 1 mm, N = 100
least count
The instrument has a positive zero error.
Main scale reading is 4 (mm) = 4 mm
Circular scale reading is 60 0.01 = 0.6 mm
Observed reading is = 4 + 0.6 = 4.6 mm
So True reading = 4.6 - 0.05 = 4.55 mm
