Energy Stores and Transfers

Energy is the property of a system that enables it to do work. This is often stated bluntly as; “energy makes thing work”.

There is a fundamental law in physics, which states that the total amount of energy in a system always remains constant. Energy cannot be created and it cannot be destroyed. Energy can, however, be transferred from one type of energy store to another.

An energy store is something that can “release” its energy at any desired time. Energy stores include a lump of coal that can exist for thousands of years before being burned and releasing heat, or a lake of water that is held behind a dam ready for release through a turbine to generate electricity when demand peaks. Coal stores chemical energy and the lake stores gravitational potential energy.

Some forms of energy cannot be stored, or can be stored only in very limited ways. These forms of energy are known as transfers, because they are the connectors between one energy store and another.

Light is, by definition, an emission: objects “give off” light. The light is not stored inside the object but is instead released when a different type of energy is transferred to the object. Put bluntly, if we heat up an object then it will glow and emit light.

Electricity is also more commonly transferred than stored: it can be stored in capacitors but not in great quantities and not for an extended period of time. But stored chemical energy, in an electric cell, can be used to “release” electricity on demand.

Here is a list of the types of energy that you are expected to know;

You may also sometimes see sound listed as an energy transfer but sound is due to the movement of particles so it can be regarded as a sub-division of kinetic energy.