Units and Measurements
3 solved JEE Physics previous year questions on Units and Measurements, each with the correct answer and a full explanation.
Q1
Given below are two statements : Statement I: In a vernier callipers, one vernier scale division is always smaller than one main scale division. Statement II: The vernier constant is given by one main scale division multiplied by the number of vernier scale divisions. In the light of the above statements, choose the correct answer from the options given below. [JEE Main 2025, 22 Jan (Shift 1)]
✓ Correct answer: b) Statement I is true but Statement II is false
Explanation(2) A vernier scale is designed such that its divisions are slightly smaller than the main scale divisions.This difference allows precise measurements by aligning a particular vernier division with the main scale.The vernier constant (least count) is actually given by: Least Count = Value of One Main Scale Division-Value of One Vernier Scale Division Thus, the correct option is: 2
Q2
For an experimental expression , where all the digits are significant. Then to report the value of y we should write
✓ Correct answer: d) y = 1330
ExplanationSignificant Figures Rule: The given numbers have minimum of 3 significant digits.The result must also be rounded to 3 significant digits.Rounding 1326.186 to 3 significant digits: (since 1326 rounds up to 1330 ) the correct answer is 1330 .
Q3
Plane angle and solid angle have : [NEET 2022]
✓ Correct answer: b) Units but no dimensions
ExplanationUnits: Plane angle has the SI unit of radian, and solid angle has the SI unit of steradian.Dimensions: They are defined as ratios of similar quantities ( for plane angle, and for solid angle), meaning they both have the dimensional formula of .
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