JEE Main202126 Aug 2021Morning ShiftPhysicsExperimental PhysicsActual
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 20 th division of the circular scale coincides with reference line. Calculate the true reading.
Options
- A5 . 20   mm
- B5 . 00   mm
- C5 . 15   mm
- D5 . 25   mm
Correct answer
C. 5 . 15   mm
Step-by-step solution
L.C. of screw Gauge = 0 . 5 50 = 0 . 01   mm Zero error of screw Gauge = 5 × L . C . = 5 × 0 . 01 = 0 . 05   mm Reading of screw gauge = main scale reading + circular scale reading × L . C . - Zero error = 5 + 20 × 0 . 01 - 0 . 05 = 5 . 15   mm