Energy changes
Energy changes form – electricity into light, food into movement.
Changing form
Energy can change from one form into another. This is an energy change. A lamp changes electrical energy into light energy. A fan changes electrical energy into movement energy.
A phone changes stored chemical energy in its battery into light (the screen), sound (the speaker) and a little heat.
Rubbing hands
Rub your hands together quickly. They get warm! Movement energy changes into heat energy because of friction. Energy chain: food → muscles → movement → heat.
Friction between brake pads and a bicycle wheel changes movement energy into heat – that is how the bicycle slows down.
Useful and wasted
A television changes electrical energy into light and sound. This is useful energy. It also gets warm. That heat is wasted energy. Good machines waste as little energy as possible.
An LED bulb changes most of its electrical energy into light. An old-style bulb wastes most of it as heat – that is why it gets so hot.
Energy is never lost
Energy is never used up or destroyed. It only changes from one form into another, or spreads out.
When a ball bounces lower and lower, its movement energy is not lost: it changes into sound and a little heat in the ball and the ground.
What I learnt
- I know that energy can change from one form into another.
- I can identify useful and wasted energy.