conservation of energy
Energy Stores and Energy Transfers:
Energy - the capacity to do work, makes everything happen
Energy Transfer -
Energy can be changed from one form to another. For example: chemical energy in food is converted to thermal energy and kinetic energy by our bodies.
Law of Conservation -
Energy cannot be created or destroyed, it can only be transferred from one form to another. Energy may change form but the total amount will remain the same.
Conservation of Energy -
Total Energy Before = Total Energy After
Sometimes energy is transferred to a store we don’t want so it seems like energy is wasted to the surroundings - we say this energy is dissipated.
Energy Transfer -
Energy can transfer between stores in four ways:
Mechanically - an object moving due to a force action on it (e.g. pushing, pulling)
Electrically - a charge moving through a potential difference (e.g. charges moving round a circuit)
By Heating - energy transferred from a hotter to a colder object (e.g. heating a pan of water on a hob)
By Radiation - energy radiating outwards from a source (e.g. energy from the Sun getting to the Earth)
Energy Efficiency:
Dissipated Energy - wasted energy that spreads out
Lubrication - used to reduce friction, wear and tear and minimise the amount of energy wasted
Efficiency - a measure of how well useful energy is transferred
Efficiency - a measure of how well useful energy is transferred
Sankey Diagram -
A diagram that shows how energy is transformed inside a device is called a Sankey Diagram. The arrows that continue to travel to the right show useful forms of energy. Arrows that diverge downwards show the forms of wasted energy.