Lesson Notes By Weeks and Term v5 - Grade 11

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

• Identify and describe common electrical faults.
• Apply systematic fault-finding techniques.
• Perform basic maintenance procedures.
• Interpret and apply safety regulations.
• Analyze circuit diagrams to troubleshoot problems.

Lesson summary

This week, we delve into the critical aspects of fault-finding, maintenance, and revision in electrical technology. These skills are not just theoretical; they are essential for ensuring the safe and efficient operation of electrical systems in homes, businesses, and industries throughout South Africa. From troubleshooting a faulty geyser in a township home to maintaining the electrical systems powering a large industrial plant in Gauteng, these skills are highly valued and contribute directly to the economy and the safety of our communities.

Lesson notes

2.1 Fault-Finding: A Systematic Approach Fault-finding is the process of identifying and locating the cause of a malfunction in an electrical system. A systematic approach is crucial for efficient and safe troubleshooting.

Here's a breakdown: Symptom Identification: Accurately identify the problem. What is not working? What are the symptoms? For example, "The light bulb doesn't turn on," or "The motor is making a strange noise." Information Gathering: Gather as much information as possible. Talk to the user, review any relevant documentation (e.g., circuit diagrams, user manuals), and observe the equipment's behaviour. Has anything changed recently?

Circuit Diagram Analysis: If available, carefully study the circuit diagram. Understand the flow of current and the function of each component.

Formulate a Hypothesis: Based on the information gathered, develop a hypothesis about the possible cause of the fault. "The bulb might be blown," or "There could be a break in the wiring." Testing and Measurement: Use appropriate test equipment (e.g., multimeter, continuity tester, insulation tester) to test your hypothesis. Start with the simplest tests first.

Fault Localization: Narrow down the location of the fault by systematically testing different parts of the circuit.

Confirmation: Once you believe you have found the fault, replace the faulty component or repair the wiring. Then, test the system to confirm that the problem is resolved.

Documentation: Record the fault, the cause, and the repair that was made. This information can be useful for future troubleshooting. 2.2 Common Electrical Faults Open Circuit: A break in the circuit, preventing current flow. This is like a broken wire. Test with a continuity tester; a working wire should have continuity (close to 0 ohms).

Short Circuit: An unintended path for current to flow, usually bypassing a load. This results in excessive current and can cause overheating, fires, and damage to equipment. Check for shorts with an ohmmeter after disconnecting the power. A low resistance reading indicates a short.

Earth Fault: A fault where a live conductor comes into contact with a metal part of the equipment or the earth. This is extremely dangerous and can cause electric shock. Use an insulation tester to check for earth faults; a good insulation should have very high resistance (Megohms).

Overload: Drawing more current than the circuit is designed to handle. This can be caused by too many appliances connected to one circuit. Overloads trip circuit breakers.

Loose Connections: Loose wires can cause intermittent problems, overheating, and arcing. Visually inspect for loose connections and tighten them. 2.3 Test Equipment Multimeter: A versatile instrument that can measure voltage, current, and resistance. Learn to use the multimeter safely and accurately. Select the correct range and connect the probes properly.

Continuity Tester: Used to check for continuity (a complete circuit). Useful for finding breaks in wires or checking if a switch is working.

Insulation Tester (Megger): Used to measure the insulation resistance of cables and equipment. Essential for identifying earth faults. Important Safety

Note: These testers often use high voltages, so handle with extreme care and follow all safety instructions.

Circuit Breaker Finder: A device to quickly identify the correct circuit breaker for a particular outlet or circuit. 2.4 Maintenance Procedures Preventative maintenance is crucial for extending the life of electrical equipment and preventing faults.

Visual Inspection: Regularly inspect equipment for signs of damage, wear, or corrosion.

Cleaning: Clean equipment to remove dust and debris, which can cause overheating.

Tightening Connections: Regularly tighten loose connections to prevent arcing and overheating.

Lubrication: Lubricate moving parts, such as motor bearings, according to the manufacturer's instructions.

Insulation Testing: Periodically test the insulation resistance of cables and equipment to identify potential earth faults.

Testing Operation: Test the operation of safety devices, such as earth leakage circuit breakers (ELCBs) or residual current devices (RCDs) to ensure they are functioning correctly. Press the test button regularly! 2.5 Worked Examples Example 1: Fault-Finding in a Simple Lighting Circuit A light bulb is not working.

Symptom: The light bulb doesn't turn on.

Information: The bulb was working yesterday. There was no power outage.

Hypothesis: The bulb is blown, or there is a break in the circuit.

Testing: Test 1: Visually inspect the bulb. If the filament is broken, the bulb is blown. Replace the bulb.

Test 2: If the bulb is not blown, use a multimeter to check for voltage at the bulb socket. If there is no voltage, there is a break in the circuit somewhere before the socket.

Test 3: Check the switch with a continuity tester. If the switch doesn't have continuity when turned on, it is faulty.

Test 4: Check the wiring for loose connections or breaks.