Level: JHS, Basic 7 | Subject: Integrated Science | Strand: Forces and Energy | Topic: Conversion and Conservation of Energy
Curriculum reference: B7.4.3.1 (NaCCA Integrated Science).
1. Energy Conversion
- Energy can change from one form to another. This is called energy conversion (or transformation).
- A device that changes energy from one form to another is an energy converter.
| Device | Energy change |
|---|---|
| Electric bulb | Electrical to light and heat |
| Electric fan | Electrical to kinetic |
| Radio | Electrical to sound |
| Dry cell (battery) | Chemical to electrical |
| Solar panel | Light (solar) to electrical |
| Car engine | Chemical to heat and kinetic |
| Hydroelectric dam | Potential to kinetic to electrical |
| Green plant (photosynthesis) | Light to chemical |
| Our body (eating food) | Chemical to kinetic and heat |
2. Conservation of Energy
- Law of conservation of energy: energy cannot be created or destroyed. It can only change from one form to another.
- The total energy before a change is equal to the total energy after the change.
- Example: a falling mango loses potential energy and gains the same amount of kinetic energy.
3. Wasted Energy and Efficiency
- In most changes, some energy turns into unwanted heat or sound. This is wasted energy, but it is not destroyed.
- A bulb gives light (useful) and heat (wasted).
- Efficiency = (useful energy output ÷ total energy input) × 100%.
- Example: a machine takes in 200 J and gives out 150 J of useful work. Efficiency = 150 ÷ 200 × 100 = 75%.
4. Saving Energy at Home
- Use LED bulbs instead of old bulbs.
- Switch off appliances when not in use.
- Cook with a covered pot to use less fuel.
Remember: Energy is never lost. It only changes form. Efficiency tells us how much of the energy is useful.
Ready to practise?
Education Always (education.inspiringalways.com). Original notes written to follow the NaCCA Basic 7 Integrated Science curriculum.