Units and Measurements Class 11 Physics

In this chapter, you will learn about Units and Measurements in Class 11 Physics, an important topic for your board exams, JEE, and NEET preparation. Master the concepts with our free resources below.

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Chapter Notes

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Key Concepts

Fundamental and derived units; SI system (7 base units: Fundamental and derived units; SI system (7 base units: m, kg, s, A, K, mol, cd)
Significant figures and rounding rules: Significant figures and rounding rules
Dimensional analysis: Dimensional analysis: dimensions of physical quantities
Errors: Errors: systematic, random, absolute, relative, percentage error
Vernier callipers and screw gauge — least count: Vernier callipers and screw gauge — least count

Important Formulas

Percentage error:

(ΔA/A) × 100%

For Z = A^p × B^q:

ΔZ/Z = p(ΔA/A) + q(ΔB/B)

Least count (Vernier):

1 MSD − 1 VSD

Solved Numerical Examples

Example 1

Problem: Calculate the percentage error in the volume of a sphere if the error in measuring its radius is 2%.

Solution: The volume of a sphere is V = (4/3)πr³. The percentage error in volume is given by ΔV/V × 100% = 3 × (Δr/r × 100%). Given Δr/r × 100% = 2%. Therefore, percentage error in volume = 3 × 2% = 6%.

Example 2

Problem: The main scale of a vernier calliper reads in mm, and 10 divisions of the vernier scale coincide with 9 divisions of the main scale. Find the least count.

Solution: 1 Main Scale Division (MSD) = 1 mm. 10 Vernier Scale Divisions (VSD) = 9 MSD, so 1 VSD = 0.9 mm. Least Count = 1 MSD - 1 VSD = 1 mm - 0.9 mm = 0.1 mm.

Daily Practice Problems (DPP)

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Multiple Choice Questions (MCQs)

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Previous Year Questions (PYQs)

Review questions from past JEE and NEET exams for Units and Measurements. Access all Physics PYQs here.

Common Mistakes

Forgetting to convert units appropriately.
Misapplying the sign convention.
Ignoring vector components in calculations.