Physics Circle home Student Login

Home›Chapters›Units, Dimensions and Measurement PYQs›Least Count, Vernier Callipers & Screw Gauge›Question 43

JEE Main 2021 (26 Aug, Shift 1) · Least Count, Vernier Callipers & Screw Gauge

Least Count, Vernier Callipers & Screw Gauge question from JEE Main 2021 (26 Aug, Shift 1)

Q43JEE Main 2021 · 26 AUG · SHIFT 1Medium

Least Count, Vernier Callipers & Screw Gauge

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.

Show answer and solution

Answer: (c)

  1. LC =0.550=0.01 mm= \dfrac{0.5}{50} = 0.01\text{ mm}
  2. 5th division on reference line when closed: zero error =+5×0.01=+0.05 mm= +5\times 0.01 = +0.05\text{ mm}
  3. Observed reading =5+20×0.01=5.20 mm= 5 + 20\times 0.01 = 5.20\text{ mm}
  4. True reading =5.20−0.05=5.15 mm= 5.20 - 0.05 = 5.15\text{ mm}. So the answer is (c).
Report a mistake

More questions on Least Count, Vernier Callipers & Screw Gauge