Energy stores and systems

A system is an object or group of objects

Systems have energy 

Energy is the ability to do work and it’s measured in joules (J)

Work is done whenever energy is transferred from one store to another

Energy cannot be created or destroyed but it can be stored, transferred, or dissipated

Energy is stored in different energy stores

• Chemical

• Kinetic energy

• Thermal

• Gravitational potential

• Nuclear

• Elastic potential

• Magnetic

• Electrostatic

There are changes in the way energy is stored a system changes

The pathways energy takes to change store are:

• Heating - due to temperature difference caused electrically or by chemical reaction

• Mechanical work (force) - a force moving an object through a distance

• Electrical work (current) - charges moving due to a potential difference

• Radiation - energy transferred as a wave (for example light)

 You need to be able to describe energy transfers in different situations

Example: A person throws a ball in the air

• Chemical energy in the person's body

• To kinetic energy of the person’s moving arm (through mechanical work)

• To kinetic energy of the moving ball (through mechanical work)

• To gravitational potential (through mechanical work) and the ball briefly stops in the air once all the energy is in the GraviPot store

• To kinetic energy of the falling ball (through mechanical work)

• Energy is transferred from one store to another by mechanical work, electrical work, by heating, or by radiation (including sound and light).energy is transferred from one store to another.

• The rate of transfer of energy depends on the difference in temperature between the heat source and the object, and properties like the object's surface area and the type of material it is made up of.

• Energy transfers may be useful transfers (e.g., electrical energy transferring to light in a light bulb) or wasteful (e.g., thermal energy transterring to the surrounding air from a light bulb).