Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Apply safety regulations (SANS standards).
• Diagnose and troubleshoot electrical faults.
• Construct and test basic electrical circuits.
• Interpret and apply circuit diagrams.
• Use hand tools and instruments proficiently.

Lesson summary

This week focuses on consolidating your understanding and practical skills in preparation for upcoming practical assessments. Practical assessments are crucial in Electrical Technology as they demonstrate your ability to apply theoretical knowledge to real-world scenarios. These assessments closely mirror tasks you might encounter as an electrician, technician, or electrical engineer. Excelling in these assessments not only improves your marks but also prepares you for the demands of the electrical industry, contributing to the development of infrastructure and technological advancements vital to South Africa.

Lesson notes

This week builds on previously learned concepts and emphasizes their practical application. We will cover the following crucial aspects: a) Safety Regulations and Procedures (SANS 10142-1): Importance: Electrical safety is paramount. Non-compliance can lead to serious injury or death. SANS 10142-1 is the South African National Standard for the wiring of premises.

Key Regulations: Isolation: Always isolate the circuit before working on it. Use a lock-out tag-out system (LOTO) to prevent accidental re-energization.

Insulation: Ensure all wires are properly insulated. Check for damage before use. Use appropriate voltage ratings for wires and components.

Earthing: Proper earthing is essential for safety. It provides a low-resistance path to ground in case of a fault, tripping the circuit breaker.

Personal Protective Equipment (PPE): Wear appropriate PPE, including safety glasses, insulated gloves, and safety shoes.

Testing: Always test the circuit after making changes to ensure it is working correctly and is safe to use. Use a multimeter to check for voltage, current, and continuity.

Example: Imagine replacing a faulty light switch in your home. Before you even touch the switch, you must switch off the power at the circuit breaker, test the switch terminals with a multimeter to ensure there's no voltage, and then wear insulated gloves while working. b)

Fault Finding and Troubleshooting: Systematic Approach: Adopt a systematic approach to fault finding: Identify the problem: What is the symptom? (e.g., the light doesn't turn on).

Gather information: Talk to the user, examine the circuit, and look for obvious signs of damage.

Develop a hypothesis: What could be causing the problem? (e.g., blown fuse, faulty switch, broken wire).

Test the hypothesis: Use a multimeter to check for voltage, current, and continuity.

Isolate the fault: Once you have identified the faulty component, isolate it from the circuit.

Repair or replace the faulty component: Replace the faulty component with a new one of the same specification.

Test the circuit: After making the repair, test the circuit to ensure it is working correctly.

Tools: Multimeter: Used to measure voltage, current, resistance, and continuity.

Continuity Tester: Used to check for continuity in a circuit.

Insulation Resistance Tester (Megger): Used to measure the insulation resistance of wires and cables. Crucial for ensuring safety and preventing leakage currents.

Example: A kettle is not heating up. First, visually inspect the kettle and its power cord for any damage. Next, check if the socket is working by plugging in another appliance. If the socket is fine, use a multimeter to check the continuity of the kettle's heating element. If there is no continuity, the element is likely faulty and needs replacement. Also, check the thermal fuse for continuity. c)

Circuit Construction and Testing: Series Circuits: Components are connected in a single path. The current is the same through all components. The total resistance is the sum of the individual resistances (R T = R 1 + R 2 + R 3 ...). The total voltage is the sum of the individual voltage drops (V T = V 1 + V 2 + V 3 ...).

Parallel Circuits: Components are connected in multiple paths. The voltage is the same across all components. The total current is the sum of the individual currents (I T = I 1 + I 2 + I 3 ...). The reciprocal of the total resistance is the sum of the reciprocals of the individual resistances (1/R T = 1/R 1 + 1/R 2 + 1/R 3 ...).

Series-Parallel Circuits: A combination of series and parallel connections. Analyze the parallel sections first to simplify the circuit.

Example (Series Circuit): Three resistors, R 1 = 10Ω, R 2 = 20Ω, and R 3 = 30Ω, are connected in series to a 12V power supply. Calculate the total resistance and the current flowing through the circuit. R T = R 1 + R 2 + R 3 = 10Ω + 20Ω + 30Ω = 60Ω I = V/R = 12V / 60Ω = 0.2A Example (Parallel Circuit): Two resistors, R 1 = 100Ω and R 2 = 200Ω, are connected in parallel to a 24V power supply. Calculate the total resistance and the total current. 1/R T = 1/R 1 + 1/R 2 = 1/100Ω + 1/200Ω = 3/200Ω R T = 200Ω / 3 = 66.67Ω (approximately) I T = V/R T = 24V / 66.67Ω = 0.36A (approximately) d)

Circuit Diagrams (Schematics): Symbols: Learn the standard symbols for common electrical components (resistors, capacitors, inductors, switches, batteries, etc.).

Interpretation: Be able to trace the flow of current through a circuit diagram.

Construction: Be able to build a circuit from a schematic diagram.

Example: A schematic shows a battery connected to a resistor and a light-emitting diode (LED) in series. You should be able to identify each component, understand its function, and build the circuit on a breadboard. Remember to include a current-limiting resistor for the LED to prevent it from burning out. e) Use of Hand Tools and Measuring Instruments: Hand Tools: Wire Strippers: Used to remove insulation from wires without damaging the conductor.