Lesson Notes By Weeks and Term v4 - JHS 2
ELECTRICITY AND ELECTRONICS
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ELECTRICITY AND ELECTRONICS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Science
Class: JHS 2
Term: 2nd Term
Week: 9
Grade code: B8.4.2.1.1
Strand code: 4
Sub-strand code: 2
Content standard code: B8.4.2.1
Indicator code: B8.4.2.1.1
Theme: FORCES AND ENERGY
Subtheme: ELECTRICITY AND ELECTRONICS
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Electricity is produced at power stations and must be transmitted over long distances to homes, schools, hospitals, factories and street lights. In Ghana, electricity may be generated at places like Akosombo (hydro), Aboadze (thermal) and solar farms, but many consumers live far away. If we tried to send electricity directly at low voltage, a lot of energy would be wasted as heat in the wires and the supply would be weak. That is why Ghana uses a transmission and distribution system with transformers, high-voltage lines, substations and distribution lines.
2.1 Meaning of Electricity Transmission Electricity transmission is the process of carrying electrical energy from the point of generation (power station) to substations over long distances, usually using high-voltage lines. After transmission, electricity is distributed to homes and businesses at safer, lower voltages.
Transmission vs Distribution Transmission: Long distance, very high voltage, fewer but larger lines (e.g., 161 kV, 330 kV). Distribution: Shorter distance within towns/communities, lower voltage (e.g., 33 kV, 11 kV, then 415/240 V to consumers).
2.2 Stages of Electricity Transmission (Generation → Consumption) Electricity supply generally follows these stages: Stage 1: Generation (Power Station) Electricity is generated using: Hydroelectric (moving water turns turbines) Thermal (burning fuel produces steam to turn turbines) Solar/Wind (renewable sources)
At the generator, the voltage is moderate (not yet extremely high). Stage 2: Step-up Transformer (At the Power Station) A step-up transformer increases the voltage to a very high value for transmission. Example: from about 11 kV to 161 kV or higher.