The pitch of the screw gauge is and there are divisions on the circular scale. When nothing is put in between the jaws, the zero of the circular scale lines divisions below the reference line. When a wire is placed between the jaws, the first linear scale division is clearly visible while the division on the circular scale coincides with the reference line. The radius of the wire is
Step 1: Given Data
Pitch
Number of divisions
Zero error divisions below the reference line
Reading of the division on the circular scale division
Step 2: Formula Used
Measured Reading = Main Scale Reading + Reading of the division on the circular scale x Least Count
Step 3: Calculate the Least Count
We know that the least count is given as,
Step 4: Calculate the Zero Error
Since the zero error is below the reference line, it is a positive zero error, which can be given as
Step 5: Calculate the Measured Reading
We know that the measured reading can be given as,
Step 6: Calculate the True Reading
The true reading can be given as,
Step 7: Calculate the Radius
Using the screw gauge we measured the diameter of the wire.
Therefore the radius of the wire is,
Hence, the radius of the wire is and therefore the correct answer is option (C).