Question

The pitch of a screw gauge is $0.5\, mm$ and there are $100$ divisions on it circular scale. The instrument reads $+2$ divisions when nothing is put in between its jaws. In measuring the diameter of a wire, there are $8$ divisions on the main scale and $83^{rd}$ division coincides with the reference line. Then the diameter of the wire is

• A. $4.05\, mm$
• B. $4.405\, mm$
• C. $3.05\, mm$
• D. $1.25\, mm$

Answer 1

Answer: (B)

$4.405\, mm$

Answer 2

$\Delta l= 0.5 \,mm$ $N= 100$ divisions Zero correction $= 2$ divisions Reading = Measured value + Zero correction $= \left(8\times0.5\right)mm + \left(83-2\right)\times\frac{0.5}{100}$ $=4mm+81\times\frac{0.5}{100}$ $=4.405\,mm$