Zusammenfassung der Ressource
P1 - Efficiency
- most energy transfers involve some waste
energy
- useful devices are only useful because
they can transfer energy from one
store to another
- some of the input energy is usually wasted by being transferred
to a useless energy store - usually the thermal energy store
- the less energy that is 'wasted' in this energy store,
the more efficient the device is said to be
- you can improve the efficiency of energy transfers
by insulating objects, lubricating them or making
them more streamlined
- EQUATION - Efficiency = useful output energy transfer/ total input energy transfer
- you might not know the energy
inputs and outputs of a device but
you can still calculate efficiency as
long as you know the power inputs
and outputs
- EQUATION - Efficiency = useful power input / total power input
- useful energy input isn't usually equal to total
energy output
- for any given example you can talk about the types of
energy being input and output
- but remember: NO device is 100% efficient and the
wasted energy is usually transferred to useless
thermal energy stores.
- Electric heaters are the exception to this. They're usually 100%
efficient because all the energy in the electrostatic energy store is
transferred to 'useful' thermal energy store
- Ultimately, all energy ends up transferred to thermal energy stores.
- E.g if you use an electric drill, its energy transfers to lots of
different energy stores, but quickly ends up all in the
thermal energy stores.