IGCSE Physics Formulas & Key Facts
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IGCSE Physics Formulas & Key Facts – Cambridge 0625/0972 [All Chapters]
IGCSE Physics (0625/0972) covers the foundation of physics—measurements, motion, forces, energy, electricity, waves, electromagnetism, and more. Hodu Academy presents a concise chapter-wise collection of the most important formulas, equations, definitions, and quick facts—all mapped to the Cambridge syllabus for top marks.
Use these formula sheets, summary tables, and revision notes for fast recall before your IGCSE exams or checkpoints. Suitable for Cambridge IGCSE, O Level, and similar international boards.
🎥 Complete Physics Video Lessons:
Get in-depth explanations and walkthroughs for every chapter on our YouTube Physics Playlist. Perfect for visual learning and step-by-step guidance!
Get in-depth explanations and walkthroughs for every chapter on our YouTube Physics Playlist. Perfect for visual learning and step-by-step guidance!
Table of Content
IGCSE Physics Syllabus Chapters
| Syllabus Section | Topics |
|---|---|
| 1. General Physics | Measurement, Motion, Forces, Energy, Work, Power, Pressure, Density |
| 2. Thermal Physics | Temperature, Thermal Expansion, Specific Heat, Latent Heat, Gas Laws |
| 3. Waves | Wave Properties, Light, Reflection, Refraction, Sound, Electromagnetic Spectrum |
| 4. Electricity & Magnetism | Electric Circuits, Current, Voltage, Resistance, Magnetism, Electromagnetic Induction |
| 5. Atomic Physics | Structure of Atom, Radioactivity, Nuclear Physics |
IGCSE Physics: Chapter-wise Formulas & Key Facts
1. General Physics
- Speed: speed = distance / time
- Velocity: velocity = displacement / time
- Acceleration: a = (v - u) / t
- Average Speed: total distance / total time
- Density: ρ = mass / volume
- Force: F = m × a
- Weight: W = m × g
- Work: Work = Force × distance (in direction of force)
- Power: Power = Work / time = Energy / time
- Kinetic Energy: KE = ½ m v²
- Potential Energy: PE = m × g × h
- Pressure: P = Force / Area; in liquids: P = h × ρ × g
- Hooke's Law: F = k × x
- Moment of Force: Moment = Force × perpendicular distance
- Principle of Moments: Clockwise moment = Anticlockwise moment (for equilibrium)
- Impulse: Impulse = Force × time = change in momentum
- Momentum: p = m × v
- Conservation of Momentum: Total p before = Total p after (in absence of external force)
Worked Examples
- Q1: A car accelerates from rest to 20 m/s in 8 s. What is its acceleration?
Solution: a = (v - u) / t = (20 - 0) / 8 = 2.5 m/s² - Q2: A box of mass 5 kg is pushed with a force of 15 N. What is its acceleration?
Solution: a = F / m = 15 / 5 = 3 m/s²
Common Mistakes & Exam Tips
- Always use SI units: convert grams to kg, cm to m, minutes to seconds.
- Write all working steps (formula, substitution, answer with units).
- Check if the question is about speed or velocity (scalar vs vector).
- Don't forget to use g = 9.8 m/s² for weight calculations unless otherwise given.
2. Thermal Physics
- Temperature Scales: °C = (°F - 32) × 5/9; K = °C + 273
- Heat Energy: Q = m × c × ΔT
- Specific Heat Capacity: c = Q / (m × ΔT)
- Specific Latent Heat: Q = m × L (L = latent heat)
- Thermal Expansion: ΔL = α × L₀ × ΔT
- Gas Laws:
- Boyle’s Law: P₁V₁ = P₂V₂ (T constant)
- Charles’ Law: V₁/T₁ = V₂/T₂ (P constant)
- Pressure Law: P₁/T₁ = P₂/T₂ (V constant)
- Combined Gas Law: (P₁V₁)/T₁ = (P₂V₂)/T₂
Worked Examples
- Q1: How much energy is needed to raise the temperature of 200g of water from 20°C to 60°C? (c = 4200 J/kg°C)
Solution: m = 0.2 kg; Q = m × c × ΔT = 0.2 × 4200 × 40 = 33,600 J - Q2: A gas is compressed from 500 cm³ to 250 cm³ at constant temperature. If the initial pressure was 100 kPa, what is the new pressure?
Solution: P₁V₁ = P₂V₂ ⇒ P₂ = (P₁V₁) / V₂ = (100 × 500) / 250 = 200 kPa
Common Mistakes & Exam Tips
- Always convert grams to kilograms (1 kg = 1000 g).
- Temperature change ΔT is always (final - initial).
- For gas laws, convert all temperatures to Kelvin.
- Use correct units for heat (Joules), pressure (Pa or kPa), volume (m³ or cm³).
3. Waves
- Wave Speed: v = f × λ
- Frequency: f = 1 / T (T = time period)
- Echo Formula: Distance = (speed × time) / 2
- Refractive Index: n = sin i / sin r = velocity in air / velocity in medium
- Law of Reflection: Angle of incidence = Angle of reflection
- Snell’s Law: n₁ sinθ₁ = n₂ sinθ₂
- Critical Angle: sin c = 1 / n (n = refractive index > 1)
- Sound: Speed of sound in air ≈ 340 m/s (at room temp.)
- Electromagnetic Spectrum Order: Radio → Microwave → Infrared → Visible → UV → X-ray → Gamma
Worked Examples
- Q1: A wave has frequency 500 Hz and wavelength 0.8 m. What is its speed?
Solution: v = f × λ = 500 × 0.8 = 400 m/s - Q2: An echo is heard 4 seconds after a shout. How far is the reflecting surface? (speed of sound = 340 m/s)
Solution: Distance = (340 × 4) / 2 = 680 m
Common Mistakes & Exam Tips
- For echoes, time is total for the sound to go and return—divide by 2 for one way.
- Use meters and seconds in calculations unless otherwise stated.
- Check if the answer needs to be rounded or in scientific notation.
- List the electromagnetic spectrum in correct order for full marks.
4. Electricity & Magnetism
- Current: I = Q / t
- Potential Difference: V = W / Q
- Ohm's Law: V = I × R
- Resistance: R = ρ × (l / A) (resistivity)
- Power: P = V × I = I² × R = V² / R
- Electrical Energy: E = P × t = V × I × t
- Series Circuits: Rtotal = R₁ + R₂ + ...
- Parallel Circuits: 1/Rtotal = 1/R₁ + 1/R₂ + ...
- Magnetic Field Around Wire: Right-hand rule
- Fleming's Left/Right Hand Rule: For force/direction in motors/generators
- Transformer: Vp/Vs = Np/Ns
- Electromagnetic Induction: E = N × (ΔΦ/Δt)
- Lenz's Law: Induced current opposes change producing it
Worked Examples
- Q1: If a current of 2 A flows for 3 minutes, how much charge flows?
Solution: Q = I × t = 2 × 180 = 360 C - Q2: The primary coil of a transformer has 200 turns and the secondary has 1000 turns. If Vp = 12 V, what is Vs?
Solution: Vs/Vp = Ns/Np ⇒ Vs = 12 × (1000/200) = 60 V
Common Mistakes & Exam Tips
- Convert time to seconds before using Q = I × t.
- Know when to use series vs. parallel formula for resistance.
- Transformers only work with AC, not DC.
- Always indicate direction with Fleming’s rules.
5. Atomic Physics
- Structure of Atom: Protons (+), Neutrons (0), Electrons (–)
- Isotopes: Atoms with same proton no., different neutron no.
- Radioactive Decay: N = N₀ e–λt
- Half-life: t1/2 = 0.693 / λ
- Alpha (α), Beta (β), Gamma (γ) Radiation: Properties, Penetrating power, Deflection in field
- Energy (Einstein): E = m c²
- Nuclear Fission & Fusion: Key differences & applications
Worked Examples
- Q1: A radioactive isotope has a half-life of 5 days. If you start with 80g, how much remains after 15 days?
Solution: 15 days = 3 half-lives. Remaining = 80 × (½)³ = 10g - Q2: What is the energy released if 0.002 kg of mass is converted to energy? (c = 3 × 10⁸ m/s)
Solution: E = m × c² = 0.002 × (3 × 10⁸)² = 0.002 × 9 × 10¹⁶ = 1.8 × 10¹⁴ J
Common Mistakes & Exam Tips
- Always use SI units for mass (kg) and time (seconds).
- For half-life, divide time by half-life to find number of cycles.
- Remember: alpha is stopped by paper, beta by aluminum, gamma only by thick lead.
- Energy from mass conversion is huge—check powers of ten!
Summary Tables & SI Units
| Quantity | Formula / Unit | SI Unit |
|---|---|---|
| Speed / Velocity | distance / time | m/s |
| Acceleration | (v - u) / t | m/s² |
| Force | m × a | Newton (N) |
| Work | F × d | Joule (J) |
| Power | Work / time | Watt (W) |
| Energy | Depends on type (Joule for KE/PE) | Joule (J) |
| Pressure | Force / Area | Pascal (Pa) |
| Charge | Q = I × t | Coulomb (C) |
| Voltage | V = W / Q | Volt (V) |
| Resistance | R = V / I | Ohm (Ω) |
| Frequency | f = 1 / T | Hertz (Hz) |
| Mass | - | Kilogram (kg) |
| Density | ρ = m / V | kg/m³ |
Key IGCSE Physics Definitions & Laws
- Scalar: Quantity with magnitude only (e.g., mass, speed, distance)
- Vector: Quantity with magnitude & direction (e.g., velocity, force, displacement)
- Newton’s First Law: Object stays at rest or in uniform motion unless acted by external force
- Newton’s Second Law: F = m × a
- Newton’s Third Law: For every action, equal and opposite reaction
- Conservation of Energy: Energy cannot be created/destroyed, only transformed
- Law of Reflection: Angle of incidence = angle of reflection
- Law of Refraction (Snell's Law): n₁ sinθ₁ = n₂ sinθ₂
- Ohm’s Law: V = I × R
- Lenz’s Law: Induced current opposes the change that causes it
- Hooke’s Law: F = k × x (spring force)
- Archimedes’ Principle: Upthrust = weight of fluid displaced
How to Revise IGCSE Physics Effectively
- Make a personal formula sheet and summary table for every chapter
- Memorize SI units and standard values
- Draw diagrams for every experiment, law, and circuit (especially ray diagrams and graphs)
- Practice as many numerical problems and MCQs as possible
- Revise key definitions, difference between scalar/vector, series/parallel, etc.
- Use mind maps, flowcharts for laws and cycles (water, carbon, etc.)
- Attempt past papers in timed conditions
Tip: Go through this page before every test—focus on equations and units for maximum marks!
Frequently Asked Questions (FAQs) – IGCSE Physics Formulas
- Q1. Is this enough for scoring high in IGCSE Physics?
Yes! If you learn, memorize, and practice with these formulas, definitions, and tables, you can solve most exam questions. Always refer to your official syllabus and textbook for any updates. - Q2. Which topics are most important?
Motion, forces, energy, waves (especially light/sound), electricity, electromagnetism, and radioactivity. Don’t ignore units and diagrams! - Q3. Do I need to remember units for all quantities?
Yes—SI units are a must for full marks in calculations and MCQs. - Q4. How should I practice?
Use these tables to solve past paper questions, check your working, and test yourself on the definitions regularly.
Bookmark Hodu Academy Physics Resources for regular updates, PDF downloads, and expert revision for every IGCSE Physics chapter!
Last modified: Saturday, 5 July 2025, 3:03 PM