18. Key Formulas — Quick Reference
Free study material · concepts, shortcuts & solved questions
Concept | Formula |
|---|---|
Celsius to Fahrenheit | F = (9/5)C + 32 |
Fahrenheit to Celsius | C = (5/9)(F − 32) |
Celsius to Kelvin | K = C + 273.15 |
Heat required (specific heat) | Q = m c ΔT |
Heat required (phase change) | Q = m L (L = latent heat of fusion/vaporisation) |
Calorimetry (heat exchange) | Heat lost by hot body = Heat gained by cold body |
Boyle's Law | P₁V₁ = P₂V₂ (constant T) |
Charles's Law | V₁/T₁ = V₂/T₂ (constant P) |
Gay-Lussac's Law | P₁/T₁ = P₂/T₂ (constant V) |
Ideal Gas Equation | PV = nRT |
First Law of Thermodynamics | Q = ΔU + W |
1 calorie (mechanical equivalent) | 1 cal = 4.184 J (≈ 4.2 J) |
Wave equation (sound) | v = f × λ |
Time period | T = 1/f |
Minimum distance to hear an echo | ≈ 17 metres (using v = 340 m/s, min. gap 0.1 s) |
Beat frequency | |f₁ − f₂| |
Human audible frequency range | 20 Hz to 20,000 Hz |
Absolute zero | 0 K = −273.15°C |
Specific heat capacity of water | 4186 J/(kg·K) [1 cal/(g·°C)] |
Latent heat of fusion of ice | 3.34 × 10⁵ J/kg |
Latent heat of vaporisation of water | 22.6 × 10⁵ J/kg |
Speed of sound in air (0°C) | 331 m/s |