Least count of screw gauge is=No.ofcirculardivisionsPitch
=1000.5mm
Least count, LC=5×10−3mm
The zero of circular scale lies 6 divisions below the line of graduation. So, zero error is positive.
Positive zero error =MSR+CSR(LC)
=0mm+6(5×10−3mm)
Diameter of wire, d=MSR+CSR(LC)–Positivezeroerror
=4×0.5mm+46(5×10−3)−6(5×10−3)mm
=2mm+40×5×10−3mm=2.2mm
Hence, diameter of wire is 220×10−2mm.