Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Identify the basic components of a circuit.
• Draw a simple circuit diagram using correct symbols.
• Explain the function of each component.
• Construct a simple series circuit.
• Differentiate between an open and a closed circuit.

Lesson summary

Electrical systems are all around us, from the lights in our homes to the appliances we use every day. Understanding how these systems work, specifically basic electrical circuits, is crucial for anyone living in South Africa, whether you’re fixing a blown fuse, designing a new electronic device, or simply understanding where your electricity comes from. Knowing the basics empowers you to be a more informed and responsible citizen. In many South African communities, load shedding is a regular occurrence, impacting daily life and economic activity.

Lesson notes

What is an Electrical Circuit? An electrical circuit is a complete path that allows electricity to flow. Think of it like a road for electricity. Just like a road needs to be complete for cars to travel, a circuit needs to be complete for electricity to flow. If there’s a break in the road, the cars can’t get through. Similarly, if there’s a break in the circuit, the electricity can't flow.

Basic Components of a Circuit: There are four essential components in a basic circuit: Power Source: This is what provides the electrical energy that drives the circuit. It's the "engine" of the road. Examples include batteries (like the ones in our torches or radios), generators (used during load shedding) or the main electrical grid (ESKOM).

The power source has two terminals: a positive (+) terminal and a negative (-) terminal. In South Africa, wall outlets provide alternating current (AC) electricity, but for simple circuits, we often use batteries that provide direct current (DC) electricity.

Conductor: This is the pathway that allows electricity to flow easily. Think of it as the asphalt on the road. Most commonly, we use wires made of copper because copper is a good conductor of electricity. Wires connect the power source to the other components in the circuit.

Load: This is the component that uses the electrical energy to perform a task. It's like the car traveling on the road. Examples include a light bulb (producing light), a resistor (controlling current), or a motor (turning something). Without a load, the circuit is essentially doing nothing useful.

Switch: This is a device that controls the flow of electricity in the circuit. Think of it as a traffic light or a gate on the road. It can either complete the circuit (allowing electricity to flow - "closed switch" or "on") or break the circuit (stopping the flow of electricity - "open switch" or "off").

Circuit Diagrams: Circuit diagrams are simplified drawings that use symbols to represent the different components of a circuit. This makes it easier to design and understand electrical circuits.

Here are some common symbols: Battery: A long line and a short line, side-by-side. The long line represents the positive (+) terminal, and the short line represents the negative (-) terminal. ( - + )

Wire: A straight line.

Light Bulb (Lamp): A circle with an "X" inside.

Resistor: A zigzag line.

Switch (Open): A line with a break in it and another line angled upwards.

Switch (Closed): A continuous straight line. Open vs.

Closed Circuits: Closed Circuit: A complete circuit with no breaks, allowing electricity to flow from the power source, through the conductor, to the load, and back to the power source. This is when the load will operate (e.g., the light bulb will light up).

Open Circuit: A circuit with a break in the path, preventing the flow of electricity. This could be due to a broken wire, a switch being open, or a blown bulb filament. If the circuit is open, the load will not operate.

Worked example

Example 1: A Simple Torch Circuit

Imagine a basic torch. It has a battery (power source), a wire (conductor), a light bulb (load), and a switch. When you turn the switch on, you are closing the circuit, allowing electricity to flow from the battery, through the wire, to the light bulb, causing it to light up. When you turn the switch off, you are opening the circuit, stopping the flow of electricity and turning the light bulb off.

Example 2: Load Shedding and Circuits

During load shedding, ESKOM interrupts the main electrical circuit supplying your home. This is like a massive switch being opened at the power station. If you have a battery-powered lamp, that circuit is still closed, and the lamp can work.