Question

A screw gauge shows 8 division on circular scale below reference line when no object is placed. Number of division on circular scale is 100 and in one complete rotation it advanced by 1mm when a copper wire is measured with it, it complete one rotation and 72 division on circular scale. Find radius of copper wire.

(1) 1.80 mm

(2) 0.90 mm

(3) 0.82 mm

(4) 1.64 mm

Answer 1

Least count =\(\tfrac{1}{100}mm\) 

positive error =+0.08 mm

Measured reading (Diameter) = 1mm+\(72\times(\tfrac{1}{100})mm\)

Original (True reading) = 1.72 – 0.08 = 1.64 mm

⇒\(\tfrac{1.64}{2}=0.82\)

So original radius = 0.82 mm