Energy is one of the most important ideas in physics. Without it, nothing would happen at all: no movement, no light, no sound, no life. Yet energy is hard to picture because it is not a "thing" you can hold. It is more like an ability: the ability to do work, to make something happen. Energy comes in many forms (motion, heat, light, electricity, chemical) and constantly changes from one form to another. The total amount of energy in the universe stays the same, but it never stops shape-shifting.
- What it isThe ability to do workMeasured in joules (J)
- Kinetic energyEnergy of motionA moving ball, a flowing river
- Potential energyStored energyHeld by gravity, chemicals, springs
- ConservationTotal amount stays constantJust changes form
- Energy in foodRoughly 4 kJ per caloriePowers your body
- Renewable sourcesSun, wind, waterWill not run out
What you will learn here
- What is energy: the basic idea and units.
- Kinetic energy: the energy a moving object carries.
- Potential energy: energy stored up, ready to be released.
- Chemical energy: energy locked into the bonds between atoms.
- Electrical energy: energy carried by flowing electric charge.
- Heat (thermal energy): the energy of particle motion in matter.
- Conservation of energy: the law that energy never disappears.
- Renewable vs non-renewable energy: where our power comes from.
Why energy matters
Every machine, every living thing and every weather event runs on energy. Cars need petrol or batteries. Plants need sunlight. You need food. The economy needs electricity from power stations. Understanding how energy works (and how to use it wisely) is one of the biggest challenges of the 21st century. Burning fossil fuels for energy is the main cause of climate change, so the world is racing to shift to renewable sources like solar, wind and nuclear.