Energy, Work and Power IGCSE Physics: Complete Guide with Memory Tips

⚡ Understanding Energy, Work and Power in IGCSE Physics

Energy, work, and power are fundamental concepts in IGCSE Physics. This comprehensive guide covers energy types, conservation laws, and calculations with proven memory techniques and practical applications.

📚 Key Theory: Energy Fundamentals

What is Energy?

• Definition: Ability to do work
• Unit: Joule (J)
• Scalar quantity: Has magnitude only
• Cannot be created or destroyed: Only transferred or transformed

Types of Energy

• Kinetic Energy (KE): Energy of motion
• Potential Energy (PE): Stored energy
• Thermal Energy: Heat energy
• Chemical Energy: Stored in bonds
• Electrical Energy: Moving charges
• Nuclear Energy: From atomic nuclei

🧠 Memory Tips and Techniques

1. Energy Types Memory: “King Philip The Chemist Eats Nuts”

• Kinetic
• Potential
• Thermal
• Chemical
• Electrical
• Nuclear

2. Work Formula Memory: “Force Distance”

• W = F × d (Work = Force × distance)
• Work done when force moves object

3. Power Formula Memory: “Work Time” or “Energy Time”

• P = W/t (Power = Work/time)
• P = E/t (Power = Energy/time)

4. Energy Conservation: “Energy Never Dies, Just Disguise”

• Energy cannot be created or destroyed
• Only changes from one form to another

📖 Work and Power

Work Done

Definition: Energy transferred when force moves object Formula: W = F × d × cos θ

• W = Work done (J)
• F = Force (N)
• d = Distance (m)
• θ = Angle between force and displacement

Conditions for Work:

• Force must be applied
• Object must move
• Movement in direction of force

Power

Definition: Rate of doing work or transferring energy Formulas:

• P = W/t (Power = Work/time)
• P = E/t (Power = Energy/time)
• P = Fv (Power = Force × velocity)

Unit: Watt (W) = J/s

🎯 IGCSE Exam Focus Areas

Common Exam Questions

1. Calculate kinetic and potential energy (4 marks)
2. Apply conservation of energy (6 marks)
3. Calculate work done and power (5 marks)
4. Analyze energy transformations (4 marks)

Key Equations to Remember

• KE = ½mv² (Kinetic energy)
• PE = mgh (Gravitational potential energy)
• W = Fd (Work done)
• P = W/t (Power)

⚡ Kinetic Energy

Formula: KE = ½mv²

• KE = Kinetic energy (J)
• m = Mass (kg)
• v = Velocity (m/s)

Key Points

• Depends on mass and velocity
• Velocity squared: Doubling speed quadruples KE
• All moving objects have kinetic energy
• Relative: Depends on reference frame

Examples

• Moving car: Large mass, high velocity
• Flying bullet: Small mass, very high velocity
• Walking person: Medium mass, low velocity

🏔️ Potential Energy

Gravitational Potential Energy

Formula: PE = mgh

• PE = Potential energy (J)
• m = Mass (kg)
• g = Gravitational field strength (9.8 m/s²)
• h = Height (m)

Elastic Potential Energy

Formula: PE = ½kx²

• k = Spring constant (N/m)
• x = Extension (m)

Examples

• Water in reservoir: High gravitational PE
• Compressed spring: Elastic PE
• Raised hammer: Gravitational PE

🔄 Conservation of Energy

Principle

Energy cannot be created or destroyed, only transferred or transformed

Energy Transformations

• Pendulum: KE ↔ PE
• Falling object: PE → KE
• Car braking: KE → Thermal energy
• Battery: Chemical → Electrical

Total Energy

Total Energy = KE + PE + Other forms In ideal systems: Total energy remains constant

📊 Energy Efficiency

Definition

Efficiency = (Useful energy output / Total energy input) × 100%

Energy Waste

• Heat: Usually wasted energy
• Sound: Often unwanted energy
• Friction: Converts useful energy to heat

Improving Efficiency

• Reduce friction: Lubrication, streamlining
• Better insulation: Reduce heat loss
• More efficient machines: Better design

🔬 Practical Applications

Renewable Energy

• Solar panels: Light → Electrical
• Wind turbines: Kinetic → Electrical
• Hydroelectric: Gravitational PE → Electrical
• Geothermal: Thermal → Electrical

Energy Storage

• Batteries: Chemical energy storage
• Pumped storage: Gravitational PE
• Compressed air: Pressure energy
• Flywheels: Kinetic energy storage

🚗 Energy in Transport

Car Energy

• Fuel: Chemical energy
• Engine: Chemical → Kinetic
• Brakes: Kinetic → Thermal
• Efficiency: Typically 20-30%

Energy Calculations

Example: Car traveling at 20 m/s

• Mass = 1000 kg
• KE = ½ × 1000 × 20² = 200,000 J
• To stop: 200,000 J converted to heat

🏠 Energy in the Home

Electrical Energy

Formula: E = Pt

• E = Energy (J or kWh)
• P = Power (W or kW)
• t = Time (s or h)

Cost of Electricity

Cost = Energy used (kWh) × Price per kWh

Energy Saving

• LED bulbs: More efficient lighting
• Insulation: Reduce heat loss
• Efficient appliances: Lower power consumption

🔋 Power Calculations

Mechanical Power

P = Fv (when force and velocity in same direction)

Electrical Power

• P = VI (Power = Voltage × Current)
• P = I²R (Power = Current² × Resistance)
• P = V²/R (Power = Voltage²/Resistance)

Power vs Energy

• Power: Rate of energy transfer
• Energy: Total amount transferred
• Analogy: Power is like speed, Energy is like distance

🌍 Energy Resources

Non-renewable

• Fossil fuels: Coal, oil, gas
• Nuclear: Uranium, plutonium
• Advantages: High energy density
• Disadvantages: Pollution, finite supply

Renewable

• Solar: Unlimited, clean
• Wind: Clean, variable
• Hydro: Reliable, location dependent
• Biomass: Carbon neutral

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