Summary
Energy is the ability to produce changes: to move something, heat it, light a lamp. There are many forms of energy —kinetic (that of motion), potential (stored by position or height), thermal, electrical, chemical, light— and all are measured in joules (J).
Energy is neither created nor destroyed, it only changes from one form into another: this is the principle of conservation of energy. A bulb turns electrical energy into light (and some heat); a person turns the chemical energy of food into movement. Energy sources can be renewable, which do not run out (the Sun, wind, water), or non-renewable, which do (oil, coal, gas).
Key points
- Energy is the ability to produce changes; it is measured in joules (J).
- Forms: kinetic, potential, thermal, electrical, chemical, light…
- Kinetic energy: that of motion. Potential: stored (height, position).
- Energy is neither created nor destroyed: it transforms (conservation).
- Devices transform one form of energy into another.
- Renewable sources (Sun, wind, water) versus non-renewable (oil, coal).
- Efficiency measures how much energy is used and how much is lost (heat).