The chapter Unit and Measurements forms the base of Physics and is highly important for JEE Main as it builds the foundation for solving numerical problems. Questions usually test concepts of units, dimensions, and error analysis.
Key Topics to Study
- Physical Quantities and Units
- Fundamental quantities: Length, Mass, Time, Current, Temperature, Luminous Intensity, Amount of Substance.
- SI Units and their conventions.
- Supplementary units (radian, steradian).
System of Units
- CGS, FPS, MKS, and SI system.
- Relation between different unit systems.
Dimensions
- Dimensional formula and dimensional equations.
- Applications:
- Checking correctness of physical equations.
- Deriving relations between physical quantities.
- Converting units from one system to another.
- Limitations of dimensional analysis.
Errors in Measurements
- Absolute error, Relative error, Percentage error.
- Combination of errors: addition, subtraction, multiplication, division, powers.
- Significant figures and rules for rounding off.
- Accuracy and Precision
- Difference between accurate and precise measurements.
- Least count of measuring instruments.
JEE Main Weightage
- Usually, 1–2 questions are asked every year from this chapter.
- Concept-based, formula-checking, or dimensional-analysis type questions are common.
- Error analysis questions are favorites for examiners.
Important Formulas
- Error propagation in addition/subtraction:
ΔZ=ΔA+ΔB\Delta Z = \Delta A + \Delta BΔZ=ΔA+ΔB - Error propagation in multiplication/division:
ΔZZ=ΔAA+ΔBB\frac{\Delta Z}{Z} = \frac{\Delta A}{A} + \frac{\Delta B}{B}ZΔZ=AΔA+BΔB - Error in powers:
ΔZZ=n⋅ΔAA\frac{\Delta Z}{Z} = n \cdot \frac{\Delta A}{A}ZΔZ=n⋅AΔA - Dimensional formula examples:
- Velocity: [M⁰ L¹ T⁻¹]
- Force: [M¹ L¹ T⁻²]
- Energy: [M¹ L² T⁻²]
Tips for JEE Preparation
- Memorize SI base units and their symbols correctly.
- Practice dimensional analysis questions regularly.
- Solve error analysis problems as they are calculation-heavy.
- Revise NCERT examples and solved problems from this unit.
- Go through past year JEE Main papers (at least last 10 years).
✅ Quick Hack for Exam: If you’re stuck, use dimensional analysis to eliminate wrong options in objective questions.
For More Information and Updates, Connect With Us
- Name: Survi
- Phone Number: +91-7488713635
- Email ID: survi@eepl.me
- Our Platforms:
- Digilearn Cloud
- EEPL Test
- Live Emancipation
- Follow Us on Social Media:
- Instagram – EEPL Classroom
- Facebook – EEPL Classroom
- https://eepl.me/blogs/
Stay connected and keep learning with EEPL Classroom!
