Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Identify basic circuit components and their functions.
• Draw a simple circuit diagram using standard symbols.
• Construct a simple working series circuit.
• Explain the difference between open and closed circuits.

Lesson summary

Hello Grade 7 Technology students! This week, we are diving into the fascinating world of electrical circuits. Understanding how electricity flows and powers our devices is crucial in today's world. From charging your phones to keeping the lights on during load shedding, electrical circuits are everywhere. In South Africa, with our ongoing challenges related to electricity supply, a basic understanding of how circuits work is not just useful, it's empowering.

Lesson notes

An electrical circuit is a complete path through which electricity can flow. Think of it like a round trip for electrons – they need a place to start, a way to travel, and a place to return to. A broken or incomplete path means no flow, and therefore, no power. The basic components of a simple electrical circuit are: Power Source: The component that provides the energy to drive the electricity through the circuit. The most common example is a battery. Batteries have two terminals, a positive (+) and a negative (-). In South Africa, we often use AA or AAA batteries in our torches and remote controls. The voltage of a battery (measured in Volts - V) tells us how much "push" it provides to the electrons. A typical AA battery is 1.5

V. Conductor: The path through which the electricity flows. Wires are usually used as conductors. Wires are made of materials like copper, which allow electricity to flow easily. This is because copper has many free electrons that can move easily when a voltage is applied. In South Africa, electrical wires are usually insulated with plastic to prevent electric shock.

Load: The component that uses the electricity to perform a task. A simple example is a light bulb. When electricity flows through the bulb, the filament inside heats up and glows, producing light. Other examples of loads could be a motor or a resistor.

Switch: A device used to open or close the circuit, controlling the flow of electricity. When the switch is closed, it completes the circuit, allowing electricity to flow. When the switch is open, it breaks the circuit, stopping the flow of electricity. Think of a light switch in your home – when you flip it on (closed), the light turns on, and when you flip it off (open), the light turns off.

Circuit Diagrams: We use symbols to represent each component in a circuit diagram. This makes it easier to draw and understand complex circuits.

Here are the standard symbols: Battery: A long line and a short line (long line is positive) |-- + - --| Wire: A straight line — Light Bulb: A circle with a cross inside ⚶ or an oval with a filament zig-zagging through it.

Switch (Open): –/ /– (the break indicates it's open)

Switch (Closed): —— (a continuous line) Open vs.

Closed Circuits: Closed Circuit: A complete path for electricity to flow. All components are connected, and the switch is closed. This allows the load (e.g., the light bulb) to function.

Open Circuit: An incomplete path for electricity to flow. There is a break in the circuit (e.g., a wire is disconnected, or the switch is open). This prevents the load from functioning.

Worked example

Example 1: Lighting up a bulb. Imagine you have a battery, a wire, and a light bulb. Connect one end of the wire to the positive (+) terminal of the battery. Connect the other end of the wire to one side of the light bulb. Then, connect another wire from the other side of the light bulb back to the negative (-) terminal of the battery. If everything is connected properly, the bulb should light up. This is because you have created a complete, closed circuit.

Example 2: Adding a switch. Now, let's add a switch to the circuit from Example

1. Cut one of the wires. Connect one end of the cut wire to one side of the switch, and connect the other end of the cut wire to the other side of the switch. Now, when the switch is closed, the circuit is complete, and the bulb will light up. When the switch is open, the circuit is broken, and the bulb will turn off. This is how you control the flow of electricity.

Example 3: Troubleshooting a non-working circuit. You have a circuit with a battery, a wire, a light bulb, and a switch.

However, the bulb is not lighting up even when the switch is closed. What could be the problem?

Possible problems include:

The battery is dead (no voltage). You can test this with a multimeter (but we won't cover that in detail now).

One or more of the wires are disconnected. Check all connections to make sure they are secure.

The light bulb is blown. Replace the light bulb with a new one.

The switch is faulty. Test the switch with a multimeter or replace it.

Guided Practice (With Solutions)

Question 1: Draw a circuit diagram of a simple circuit with a battery, a wire, and a light bulb. The switch should be open.

Solution:

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|-- + - --| ——— ⚶ –/ /–

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