What are Physical Quantities?
Physical Quantities
This section introduces the concept of physical quantities and their properties.
What is a physical quantity?
- A physical quantity is any measurable property.
- It has a numerical magnitude and a unit of measurement.
Properties of a physical quantity
- A physical quantity must have both magnitude and unit.
- Example: Height of a student is 165 cm, where 165 is the numerical magnitude and cm is the unit.
Categories of physical quantities
- Base Quantities: Length, mass, time, temperature, intensity of light, electric current, amount of substance.
- Derived Quantities: Area, volume, velocity, acceleration, force, pressure, momentum, electric charge.
Units for Physical Quantities
This section discusses the universally adopted system of units for measuring physical quantities.
Importance of units
- Units provide a standard with which quantities can be compared and expressed.
- Units allow for universal sharing of knowledge and findings in different fields.
International System of Units (SI)
- The SI system was accepted during the eleventh General Conference on Weights and Measures in 1960.
- SI stands for System International.
Base Units
- Length: Meter (m)
- Time: Second (s)
- Mass: Kilogram (kg)
- Electric Current: Ampere (A)
- Temperature: Kelvin (K)
- Amount of Substance: Mole (mol)
- Intensity of Light: Candela (cd)
Derived Units
- Derived units are defined in terms of base units.
- Examples include velocity (m/s), acceleration (m/s²), force (N), pressure (Pa), momentum (kg·m/s), charge (C), magnetic flux density (T).
Measurement Techniques
This section explains different techniques for measuring physical quantities accurately.
Length Measurement
- Meter Rule: Used to measure length or distance between two points. Smallest reading is 1mm.
- Measuring Tape: Used for greater lengths, measured in cm and inches.
- Vernier Caliper: Provides accuracy of more than 1mm. Least count is 0.1mm.
Zero Error in Measurements
This section discusses the concept of zero error in measurement instruments.
Vernier Caliper
- To achieve accurate measurements, we need to find the zero error of the instrument.
- Zero error can be added or subtracted from obtained readings to obtain accurate results.
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