Question

How do you account for positive zero error for calculating the correct diameter of wires?

Answer 1

If the zero lines, marked on a circular scale, is below the reference line of the main scale, then there is a positive zero error and the correction is negative. In figure 5th, circular scale division is coinciding with the reference line.
∴ Correction = – Coinciding division of C.S. × L.C.
= – 5 × 0.001 cm
= – 0.005 cm
If the observed diameter is 0.557 cm, then:
Corrected diameter
= Observed diameter + Correction
= 0.557 cm – 0.005 cm
= 0.552 cm