Energy Management
Primary 6 · Science and Elementary Technology
Energy Management
Lesson 2 of 6
15 min
Let's begin
The power goes off during a storm, and Keza reaches for her torch. Click! A beam of light fills the room.
But where did that light come from? The torch was dark a moment ago. The answer is hidden inside the batteries: energy was waiting there in another form.
Energy can change from one form to another. This is called energy transformation or energy conversion. Scientists have found that energy is never made out of nothing and never disappears: it only changes form or moves from one object to another. This is the law of conservation of energy.
| Device or activity | Energy going in | Energy coming out |
|---|---|---|
| Torch | Chemical (in the dry cells) | Electrical, then light (and a little heat) |
| Solar panel | Light | Electrical |
| Radio | Electrical | Sound |
| Electric kettle or iron | Electrical | Heat |
| Electric fan or motor | Electrical | Kinetic (movement) |
| Charging a phone | Electrical | Chemical (stored in the battery) |
| Charcoal stove or burning match | Chemical | Heat and light |
| Moto engine | Chemical (petrol) | Kinetic, plus heat and sound |
| Your body | Chemical (food) | Kinetic and heat |
| Bicycle dynamo lamp | Kinetic | Electrical, then light |
We can show an energy change with arrows. Write the first form on the left and the form you use on the right:
Not all the energy ends up in the form we want. An old filament bulb becomes very hot: most of its electrical energy turns into heat we do not need, and only a small part becomes light. The heat is wasted energy; it spreads into the surroundings. A moto engine wastes energy as heat and noise. An LED bulb gives the same light while wasting much less energy as heat, so it is more efficient.
Open the Energy Forms and Changes simulation and choose the Systems screen. Build a chain: pick the sun, a solar panel and a light bulb, or running water, a generator and a water heater. Tick "Energy Symbols" to watch small blocks of energy change form as they travel along your chain.
Tip
Ask two questions: What goes IN? What comes OUT?
The first form in the chain is the energy you feed in; the last form is the energy you use. Anything else that comes out, such as unwanted heat or noise, is wasted.
Try each one on your own first, then tap Show answer to check.
Write the energy chain for a radio that runs on batteries.
Answer: chemical → electrical → sound.
What energy change happens in a solar panel?
Answer: Light energy → electrical energy.
A moto is moving. Name its useful energy and two kinds of wasted energy.
Answer: Useful: kinetic (movement). Wasted: heat and sound.
Write the energy chain for a hydroelectric power station.
Answer: potential energy of stored water → kinetic energy of falling water → electrical energy.
Why is an LED bulb more efficient than a filament bulb?
Answer: It turns more of its electrical energy into light and wastes much less as heat.
What you learned today
Sources and credits
Quick check
Match each device or activity to its energy change.
Tap one on the left, then its partner on the right.
