SR Unit and SI Prefix Lecture Notes

Introduction

• SR Unit: International unit for quantities.
• Seven Major Quantities: Foundation for all other units.

SI Units for Major Quantities

• Length:
  • Unit: Meter
  • Symbol: m (lowercase)
• Mass:
  • Unit: Kilogram
  • Symbol: kg (lowercase k)
• Time:
  • Unit: Second
  • Symbol: s (lowercase)
• Temperature:
  • Unit: Kelvin
  • Symbol: K (uppercase)
• Amount of Substance:
  • Unit: Mole
  • Symbol: mol
• Electric Current:
  • Unit: Ampere
  • Symbol: A
• Luminous Intensity:
  • Unit: Candela
  • Symbol: cd

Derived Units

• Area:
  • Formula: Length × Length
  • Unit: Meter² (m²)
• Volume:
  • Formula: Length × Length × Length
  • Unit: Meter³ (m³)
• Speed/Velocity:
  • Formula: Distance/Time
  • Unit: Meter/Second (m/s)
• Acceleration:
  • Formula: Change of Speed/Time
  • Unit: Meter/Second² (m/s²)
• Force:
  • Formula: Mass × Acceleration
  • Unit: Kilogram Meter/Second² (kg·m/s²)
  • Alternative Notation: kg·m·s⁻²

Scientific Notation and SI Prefixes

• Used for very large or small numbers in physics and chemistry.
• Common SI Prefixes:
  • Giga: 10⁹, Symbol: G
  • Mega: 10⁶, Symbol: M
  • Kilo: 10³, Symbol: k
  • Centi: 10⁻², Symbol: c
  • Milli: 10⁻³, Symbol: m
  • Micro: 10⁻⁶, Symbol: µ (mu)
  • Nano: 10⁻⁹, Symbol: n
  • Pico: 10⁻¹², Symbol: p

Examples of Using SI Prefixes

• Milli:
  • Example: 10⁻³ → 1.2 mg (milligram)
• Nano:
  • Example: 10⁻⁹ → 5.22 nm (nanometer)
• Giga:
  • Example: 10⁹ → 8.9 GHz (gigahertz)

Conclusion

• SI Units and prefixes simplify representation of large and small values in scientific measurements.
• Importance in physics and chemistry for accuracy and ease of communication.

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