Energy stores and transfers

Energy can be stored and transferred. It cannot be created or destroyed. The total energy of a system stays the same. Energy is transferred from a hot object to a cool one by conduction or radiation.

Stores of energy

Energy can be stored in different ways, including:

  • kinetic energy
  • internal energy
  • elastic potential energy
  • gravitational potential energy
  • electrical energy
  • magnetic energy

Kinetic energy

Moving things have kinetic energy. The more mass a thing has and the faster it moves, the more kinetic energy it has. All moving things have kinetic energy, even very large things like planets, and very small ones like atoms.

Internal energy

Cup of tea.
A hot cup of tea has more internal energy than a cold cup of tea

All objects have internal energy. This includes:

  • energy caused by the movement of particles in the object, sometimes called thermal energy
  • energy due to the bonds between particles, sometimes called chemical energy

Elastic potential energy

Some objects can change shape reversibly. Rubber balls, springs and elastic bands are like this. When a rubber ball is stretched or squashed, it can regain its shape again. Elastic potential energy is stored in stretched or squashed materials.

A man pulling back a catapult.
Elastic potential energy will be stored in this catapult when its bands are stretched

Gravitational potential energy

When an object is moved higher, it gains gravitational potential energy. The amount of energy it gains depends upon:

Boulders balanced on top of rocks.
These rocks store gravitational potential energy because of their height above the ground

Electrical energy

Some objects carry electrical charges and create electric fields. These charged objects can exert forces on each other. You get an electric current when charged particles move through a wire.

Magnetic energy

Some objects can be magnetised and create magnetic fields. They can exert forces on other magnetised objects, or on magnetic materials.

Iron filings showing the magnetic field of a bar magnet.
The magnetic field created by this bar magnet is shown using iron filings