: Systems Engineering – Unit 3 Revision Study Guide Electrical & Energy Systems 1. The Engineering Process & Systems Thinking 1.1 The Engineering Process Stages You must know the sequence and purpose of each stage: 1. Investigate & design 2. Plan 3. Produce a solution 4. Test and diagnose 5. Evaluate and report 6. Modify and improve Once a system is built, the next stage is always “Test and diagnose”. 1.2 IPO Diagrams (Input–Process–Output) Used to analyse and explain systems. Example: Home Security Alarm • Inputs: Motion sensors, door switches, keypad input • Process: Microcontroller compares input to programmed logic • Outputs: Alarm siren, alert light, SMS notification Be ready to label inputs, processes, and outputs clearly. 2. Energy Sources & Sustainability 2.1 Renewable vs Non-Renewable • Renewable: Solar, wind, hydro, tidal, biomass, geothermal • Non-renewable: Coal, oil, gas, nuclear (alternative but not renewable) Geothermal energy comes from heated groundwater. 2.2 Advantages & Disadvantages (Exam Favourite) Wind Power – Advantages • Renewable • Zero greenhouse emissions during operation • Low operating cost • Scalable • Reduces fossil fuel dependence Coal Power – Disadvantages • High CO₂ emissions • Non-renewable • Air pollution • Thermal inefficiency • Environmental damage You will be asked to: • Compare energy sources • Justify one over another • Give an opinion with reasoning 3. Energy Transformations Know energy chains in order: Examples • Wind turbine: Kinetic → Mechanical → Electrical • Hydro power: Potential → Kinetic → Mechanical → Electrical • Solar PV: Radiant → Electrical 4. Efficiency Calculations HIGH PRIORITY 4.1 Formula Efficiency= Useful output energy Total input energy × 100% 4.2 Combined Efficiency Multiply efficiencies as decimals: Example: • Solar panel: 40% → 0.40 • Battery: 80% → 0.80 0.40 × 0.80 = 0.32 = 32% Combined efficiency = 32% 5. Electrical Fundamentals 5.1 Current Types • AC (Alternating Current): Household power, wind turbines • DC (Direct Current): Batteries, solar panels 5.2 Frequency & Period 1 𝑓 = 𝑇 • Australia mains electricity = 50 Hz • Direction changes 50 times per second Example: • Period = 0.005 s 𝑓 = 1 ÷ 0.005 = 200 Hz 6. Power, Work & Energy Calculations 6.1 Power 𝑊 𝑃 = or𝑃 = 𝑉 × 𝐼 𝑡 Example: • 1,000,000 J in 50 s 𝑃 = 1,000,000 ÷ 50 = 20,000 W 6.2 Work 𝑊 = 𝐹 × 𝑑 Example: • 2000 N × 10 m = 20,000 J 7. Batteries & Electrical Storage 7.1 Series vs Parallel • Series: Voltage adds • Parallel: Capacity (Ah) adds Example: • 4 × 12 V batteries in series = 48 V 7.2 Battery Runtime Total energy Time (h)= Power of load 8. Circuit Theory 8.1 Ohm’s Law 𝑉 = 𝐼 × 𝑅 8.2 Resistance • Series: 𝑅𝑇 = 𝑅1 + 𝑅2 + 𝑅3 • Parallel: 1 1 1 = + 𝑅𝑇 𝑅1 𝑅2 8.3 Capacitors • Series: inverse rule • Parallel: add values directly 9. Electrical Components & Symbols You must identify: • Resistor • Variable resistor (potentiometer) • Capacitor • Cell / Battery • LDR (light-dependent resistor) • LED • Diode • Thermistor • Switch types: SPST, SPDT, DPDT LED does not detect light LDR, phototransistor do 10. Transformers Formula 𝑉 𝑠 𝑁 𝑠 = 𝑉 𝑝 𝑁 𝑝 Example: • 40 primary, 800 secondary • Input = 240 V 𝑉 𝑠 = 240 × (800 ÷ 40) = 4800𝑉 Used to step up voltage → reduce current → reduce power loss 11. Power Transmission Why Voltage Is Stepped-Up • Reduces current • Minimises power loss as heat • Improves efficiency • Allows thinner cables • Enables long-distance transmission 12. Power Electronics Rectifier • Converts AC to DC H-Bridge + PWM • Technique: Pulse Width Modulation (PWM) • Purpose: Convert DC into simulated AC & control motor speed 13. Semiconductors • Doping: Adding impurities to silicon • Creates diodes and transistors • Enables controlled current flow 14. Safety & Standards Before using 230 V power tools: Must have a current electrical safety tag 15

What are the stages of the Engineering Process?

1. Investigate & design 2. Plan 3. Produce a solution 4. Test and diagnose 5. Evaluate and report 6. Modify and improve

What is the purpose of IPO diagrams in systems analysis?

To analyse and explain systems by identifying Inputs, Processes, and Outputs.

List three examples of renewable energy sources.

Solar, wind, hydro.

What is the main disadvantage of coal power?

High CO₂ emissions and non-renewable.

Know the energy transformation sequence for hydro power.

Potential → Kinetic → Mechanical → Electrical

What is the formula for calculating efficiency?

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

How do you calculate combined efficiency?

Multiply individual efficiencies as decimals.

What type of current is typically found in batteries?

DC (Direct Current) - Direct current is used in batteries and solar panels.

What is the frequency of Australia’s mains electricity?

50 Hz.

What does Ohm's Law state?

V = I × R.

In a series circuit, how is total resistance calculated?

RT = R1 + R2 + R3.

What happens to voltage in a series arrangement of batteries?

Voltage adds up.

What does a rectifier do?

Converts AC to DC.

What is the purpose of using transformers in power transmission?

To step up voltage, reduce current, and minimize power loss.

Why is voltage stepped up during power transmission?

To reduce current, minimize power loss as heat, and improve efficiency.

What is the function of an H-Bridge in power electronics?

To convert DC into simulated AC and control motor speed.

What must be done before using 230 V power tools?

Must have a current electrical safety tag.

What should you remember to do for calculation questions in the exam?

Always show working for calculation questions.

What should you include when justifying answers in exam questions?

Write full sentences and include units (W, V, Hz, Ω).