Verified Solution • 2025–26 Session moderate

QJEEM21Phbff0: JEE Main 2021 Physics - Class 11 JEEM21Phbff0 Solution: In a Screw Gauge, fifth division of the circular scale…

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.

Multiple Choice Options

  • A 5.00 mm
  • B 5.25 mm
  • C 5.15 mm
  • D 5.20 mm

Step-by-Step Verified Solution

Least count (L. C.) = 0.550

True reading = 5+0.550×20−0.550×5

=5+0.550(15)=5.15 mm

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