Question

In an experiment with a screw gauge with a pitch of $0.5\,mm$ and a circular scale with $50$ divisions is used to measure the thickness of a thin sheet of Aluminium. Before starting the measurement, it is found that when the two jaws of the screw gauge are brought in contact, the $45^{t h}$ division coincides with the main scale line and that the zero of the main scale is barely visible. Find the thickness of the sheet if the main scale reading is $0.5\,mm$ and the $25^{t h}$ division coincides with the main scale line?

• A. 0.70 mm
• B. 0.50 mm
• C. 0.75 mm
• D. 0.80 mm

Answer 1

Answer: (D)

$LC=\frac{0.5}{50}=0.01 \, mm$
Zero error $=0.50-0.45=-0.05$
Thickness $=\left(0.5 + 25 \times 0.01\right)+0.05$
$=0.5+0.25+0.05$
$=0.8 \, mm$