Units and Measurement

Overview

Units and Measurement forms the foundational chapter of physics and is essential for MAHA TET Paper II (Mathematics and Science). This topic tests your understanding of how physical quantities are expressed, the International System of Units (SI), and practical measurement techniques for length, mass, time, and temperature.

For the exam, expect direct questions on SI base units, their symbols, conversion between units, and the correct use of measuring instruments. Questions often appear as fill-in-the-blanks, match-the-columns, or simple numerical conversions. Mastery here also supports later topics like motion, force, and heat, where correct unit handling is critical.

Students must be able to distinguish between fundamental and derived quantities, recall SI units with correct symbols, perform unit conversions confidently, and understand the principles behind common measuring instruments used in school laboratories.

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Key Concepts

• **Physical Quantity**: Any quantity that can be measured and expressed in numbers with a unit (e.g., length = 5 metres).

• **Fundamental (Base) Quantities**: Quantities that are independent and cannot be derived from other quantities. SI has seven base quantities: length, mass, time, electric current, temperature, amount of substance, and luminous intensity.

• **Derived Quantities**: Quantities obtained by combining fundamental quantities through multiplication or division (e.g., speed = length ÷ time, area = length × length).

• **SI System (Système International)**: The internationally accepted system of units adopted in 1960. India officially uses SI units.

• **Standard Unit**: A fixed and universally accepted reference for measurement. For example, the metre is defined based on the speed of light.

• **Precision vs Accuracy**: Precision refers to how close repeated measurements are to each other; accuracy refers to how close a measurement is to the true value.

• **Least Count**: The smallest measurement that an instrument can make. For a standard ruler, least count = 1 mm = 0.1 cm.

• **Significant Figures**: The meaningful digits in a measured value that indicate the precision of measurement.

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Formulas / Key Facts

### SI Base Units for MAHA TET

| Physical Quantity | SI Unit | Symbol | |-------------------|---------|--------| | Length | metre | m | | Mass | kilogram | kg | | Time | second | s | | Temperature | kelvin | K | | Electric Current | ampere | A | | Amount of Substance | mole | mol | | Luminous Intensity | candela | cd |