In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 50 divisions on the circular scale, and the main scale moves by 0.5 mm on a complete rotation. For a particular observation the reading on the main scale is 5 mm and the 20th division of the circular scale coincides with reference line. Calculate the true reading.
- (A)5.25 mm
- (B)5.15 mm✓ Correct
- (C)5.20 mm
- (D)5.00 mm
Answer: (B)
Solution
The main scale advances mm per rotation and the circular scale has divisions, so
With the ratchet closed the fifth division sits on the reference line, so the zero error is mm. The observed reading is
and the true reading is the observed reading less the zero error,
With the ratchet closed the fifth division sits on the reference line, so the zero error is mm. The observed reading is
and the true reading is the observed reading less the zero error,
JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Single correct option