Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify and safely use at least three types of pliers.
• Demonstrate how to measure voltage, current, and resistance with a multimeter.
• Explain the importance of Personal Protective Equipment (PPE).
• Understand basic First Aid for electrical shock.
• Identify and mitigate hazards with hand tools.

Lesson summary

This week, we delve deeper into the essential aspects of workshop safety, focusing on specific tools and measuring instruments crucial for electrical work. Safety in the workshop isn't just about following rules; it's about understanding the potential hazards and proactively preventing accidents. Many South African communities rely on skilled electricians for everything from household wiring to industrial maintenance. A strong foundation in safety and the correct use of tools and instruments is vital for protecting yourself, your colleagues, and the public. Lack of safety knowledge leads to injuries, damaged equipment, and unsafe electrical installations, which can have dire consequences.

Lesson notes

2.1 Pliers: Types, Uses, and Safety Pliers are indispensable hand tools for electricians. Different types are designed for specific tasks.

Side-Cutting Pliers (Linesman Pliers): Used for cutting wires, stripping insulation (with integrated strippers in some models), and gripping.

Usage: Position the wire between the cutting jaws, apply steady pressure, and squeeze the handles firmly.

Safety: Never use them to cut live wires unless they are properly insulated and rated for the voltage. Ensure the cutting blades are sharp and free from damage. Do not extend the handles for extra leverage as this can damage the pliers or cause injury. Wear safety glasses to protect your eyes from flying wire pieces.

Long-Nose Pliers (Needle-Nose Pliers): Ideal for reaching into tight spaces, bending wires, and manipulating small components.

Usage: Use the narrow jaws to grip and bend wires. Avoid excessive force, as the tips can bend or break.

Safety: These pliers are not designed for cutting thick wires. Avoid using them on hard materials that could damage the tips. Never use them to tighten nuts or bolts.

Water Pump Pliers (Multi-Grip Pliers): Adjustable pliers used for gripping and turning pipes, nuts, and bolts. Although more often used in plumbing, they can be useful in electrical installations involving conduit and cable glands.

Usage: Adjust the jaw opening to fit the object. Ensure a firm grip before applying force.

Safety: Be careful not to damage the object being gripped, especially electrical conduit. Avoid over-tightening. Keep hands clear of the jaws to prevent pinching.

Insulated Pliers: These pliers are designed with insulated handles to protect the user from electric shock. They are marked with a voltage rating.

Usage: Same as above but MUST be used on potentially live circuits (if qualified and authorized).

Safety: NEVER use insulated pliers if the insulation is damaged or compromised. Always check the voltage rating before working on a circuit. The insulation is there to protect you, but only if it is in good condition. 2.2 The Multimeter: Your Electrical Swiss Army Knife A multimeter is an essential instrument for any electrician. It can measure voltage, current, and resistance. Understanding how to use it safely and accurately is crucial.

Voltage Measurement: Measures the electrical potential difference between two points in a circuit.

Procedure: Select the appropriate voltage range (AC or DC) and a value higher than the expected voltage. If unsure, start with the highest range and work down. Plug the black lead into the COM (common) terminal and the red lead into the V (voltage) terminal. Connect the probes in parallel with the component or circuit you want to measure. Read the voltage value on the display.

Safety: Never connect the probes across a circuit in series when measuring voltage. This will short circuit the power supply. Be careful not to touch any exposed metal parts of the circuit or probes. Always disconnect the power before making connections.

Current Measurement: Measures the flow of electrical charge through a circuit.

Procedure: Select the appropriate current range (AC or DC) and a value higher than the expected current. If unsure, start with the highest range and work down. Plug the black lead into the COM (common) terminal and the red lead into the A (current) terminal. Some multimeters have different A terminals for different current ranges (e.g., mA and A). Disconnect the circuit at the point where you want to measure the current. Connect the multimeter probes in series with the circuit, completing the circuit path. Read the current value on the display.

Safety: Never connect the multimeter probes in parallel across a voltage source when measuring current. This will cause a short circuit and can damage the multimeter and the circuit. Make sure the circuit is de-energized before breaking the circuit to insert the multimeter. Use the correct current terminal on the multimeter and be aware of its current limits. Some multimeters use fuses to protect the current ranges.

Resistance Measurement: Measures the opposition to the flow of electrical current.

Procedure: Select the resistance (Ω) range on the multimeter. Plug the black lead into the COM (common) terminal and the red lead into the Ω (resistance) terminal. Disconnect the component from the circuit. Connect the probes across the component you want to measure. Read the resistance value on the display.

Safety: Never measure the resistance of a component that is connected to a live circuit. This can damage the multimeter and give an inaccurate reading. Always disconnect the power source before measuring resistance.

Example 1: Voltage Measurement A learner wants to measure the voltage of a 12V DC battery. The multimeter is set to the 20V DC range. The black lead is connected to the negative terminal of the battery, and the red lead is connected to the positive terminal. The display shows 12.3V.