Lesson Notes By Weeks and Term v4 - SHS 2
ELECTRICAL SYSTEMS DESIGN
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ELECTRICAL SYSTEMS DESIGN
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Subject: Applied Technology
Class: SHS 2
Term: 2nd Term
Week: 13
Grade code: 2.5.1.LI.3
Strand code: 5
Sub-strand code: 1
Content standard code: 2.5.1.CS.1
Indicator code: 2.5.1.LI.3
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRICAL SYSTEMS DESIGN
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Electricity is a vital part of our daily lives in Ghana, powering everything from the light bulb in our room to the television in the living room and the mobile phones we use to connect with family. However, for electricity to be useful and safe, it must be properly controlled and distributed within our homes. This lesson introduces the fundamental building blocks of a domestic electrical system. We will explore the specific materials, accessories, and safety devices that an electrician uses to safely bring power from the ECG/NEDCo poles to the sockets on our walls.
This topic can be broken down into three main areas: (A) The Materials We Use, (B) The Path Power Takes, and (C) How We Stay Safe. Part A: Materials and Accessories for House Wiring (Indicator 2.5.1.AS.3)
To wire a house, we need more than just wires. We need a system of components working together. Cables: A cable is not just a wire. It consists of two main parts: Conductor: The inner part, usually made of copper, that allows electricity to flow easily. Insulation: The outer plastic (PVC) coating that prevents the electricity from escaping and causing shocks or short circuits. It also helps in identifying wires (e.g., Brown for Live, Blue for Neutral, Green/Yellow for Earth).
Common Cable Sizes and Their Uses in Ghana: Cable sizes are measured by the cross-sectional area of the conductor in square millimetres (mm²). A larger area means the cable can safely carry more current.
| Cable Size (mm²) | Common Use | Typical Current Rating | Explanation | | :--------------- | :---------------------------------------- | :--------------------- | :----------------------------------------------------------------------------------------------- | | 1.5 mm² | Lighting circuits | ~13 Amperes | Used for devices that draw low current, like light bulbs and ceiling fans. | | 2.5 mm² | Socket outlets (Ring Final Circuit) | ~20 Amperes | Used for general-purpose sockets where you plug in TVs, chargers, blenders, etc. | | 4.0 mm² | High-power single outlets, small cookers | ~27 Amperes | Used for devices that draw more power, like a water heater or a small electric oven. | | 6.0 mm² | Electric cookers, large water heaters | ~35 Amperes | For high-power kitchen appliances that require a dedicated circuit. | | 10.0 mm² / 16.0 mm² | Main supply from meter to consumer unit | ~50-70 Amperes | These are the "main arteries" that bring all the power into your house's distribution board. |