Lesson Notes By Weeks and Term v4 - JHS 3
ENERGY
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ENERGY
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Subject: Science
Class: JHS 3
Term: 2nd Term
Week: 6
Grade code: B9.4.1.2.1
Strand code: 4
Sub-strand code: 1
Content standard code: B9.4.1.2
Indicator code: B9.4.1.2.1
Theme: FORCES AND ENERGY
Subtheme: ENERGY
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Energy is used every day in our homes, schools, shops and industries—especially electrical energy for lighting, fans, televisions, refrigerators, phone charging and ironing. In Ghana, electricity bills are based mainly on how many units (kWh) of electrical energy we consume. Understanding how to calculate energy consumed helps learners: estimate electricity cost at home, use appliances wisely to reduce bills, make informed decisions about energy conservation.
A. Meaning of Power and Energy Power (P) is the rate at which energy is used or transferred. Unit: watt (W) \(1\,\text{W} = 1\,\text{J/s}\)
Electrical Energy (E) is the total amount of electrical work done or energy used. Units: joule (J) in science, and kilowatt-hour (kWh) for electricity billing.
Electricity companies commonly use kWh because it gives a convenient “unit” for large energy use.
B. Key Formulae for This Indicator 1) Electrical power from current and voltage \[ P = IV \] Where: \(P\) = power (W) \(I\) = current (A) \(V\) = voltage (V)