Energy can transfer or move from one store to another in different ways. Devices such as lamps and heaters may be involved, or processes such as combustion. For example, energy can be transferred:
Some objects are hotter than others. Energy is transferred from the hotter object to the cooler one, and the difference in temperature between them decreases.
Energy can be transferred mechanically through the movement of the parts in machines, and when the motion or position of an object changes. Sound waves and seismic waves (formed during earthquakes) are mechanical waves that transfer energy through materials and from place to place.
Energy is transferred when an electrical circuit is complete. A simple circuit may consist of a battery, lamp and wires. Internal energy stored in the battery is transferred to moving charged particles in the wire.
Visible light, infrared light, microwaves and radio waves are forms of radiation. They are carried by waves (although unlike sound, these are not mechanical waves and can travel through empty space). Electric lamps and burning fuels transfer visible and infrared light to the surroundings.
When an object falls the gravitational potential energy it possessed is converted to kinetic energy. When it has fallen half of the way down, half of the energy will have been transferred and so on.
Food contains internal energy stored in the bonds between particles. This is sometimes called chemical energy. This is converted into the energy all living organisms need during respiration. This conversion is similar to burning, for example wood. Here internal energy in the wood is converted into heat and light given out by the flames.