P1.2.1 - AQA GCSE Physics Unit 1

P1.2.1	Energy transfers and efficiency
	a) Energy can be: transferred usefully, stored, or dissipated, but cannot be created or destroyed.	This can be termed the 'conservation of energy'. You should recall this statement - learn it by heart! You need to understand and identify the various 'types' of energy that there are... the forms energy takes in our natural world. Sankey diagrams represent these energy changes. 'Wasted' energy is any energy that is not usefully transferred.
	b) When energy is transferred only part of it may be usefully transferred, the rest is 'wasted'.
	c) Wasted energy is eventually transferred to the surroundings, which become warmer. The wasted energy becomes increasingly spread out and so becomes less useful.	If energy is in a concentrated form we can make use of it easily - when it is 'dissipated' - shared out among lots of particles - it becomes difficult to harness. This dissipated energy makes the particles it is absorbed by a little warmer.
	d) To calculate the efficiency of a device using: efficiency = (useful energy out /total energy in) x 100% OR efficiency = (useful power out /total power in) x 100%