p7 Flashcards
energy stores
chemical
thermal
kinetic energy
gravitational
elastic
nuclear
electrostatic
magnetic
energy transfers
mechanically (forces)
electrically ( current)
heating (particles or radiation)
what is an energy store
indication of the amount of energy in joules
law of energy
conserved
cannot be created or destroyed
describe energy stores in a moving car
mechanically
FROM:
- no k.e
- more chemical store
- less thermal energy
TO:
- some k.e
- less chemical energy
- more thermal energy
describe energy stores in gymnastics
mechanically
FROM:
- no elastic store
- more k.e
- more g.p.e
TO:
- more e.pe
- no k.e
- low g.pe
describe energy stores in ball thrown up
mechanically
FROM:
- more k.e
- less gpe
- less thermal store
TO:
- no k.e
- more gpe
- more thermal store
describe energy stores when dropping sunglasses
mechanically
FROM:
- more k.e
- less thermal store (sand cooler at first)
TO:
- no ke
- high thermal energy (sand gets hotter)
when a current /charge flows, energy is transferred from…
… chemical store of a battery
… chemical store of à nuclear power station (fuel used in mains electricity)
how microwaves work
transfer energy electrically from heating
how hairdryers work
electrical energy produced by heating radiation (infrared)
mechanical energy from fan to move and dry hair
where is chemical energy found
fuel/ oxygen
batteries
describe how electrical kettle works
electrically by heating
FROM:
- high chemical energy
- low thermal energy
TO:
- low chemical energy
- high thermal
-
energy can be increased in a thermal store by:
burning fuel
using electrical current to transfer energy
describe energy transferred in a storage heater
FROM:
high concrete energy
low room thermal energy
TO:
low concrete thermal energy
high room thermal energy
different ways energy can be dissipated
friction between parts of à car engine
conduction between plastic parts of à kettle
radiation from the front of an oven
how to reduce dissipation
lubrication (reduce friction)
insulation (reduce heat loss)
rate of cooling on thicker walls
less temperature lost
takes long to cool down
lower rate of cooling
rate of cool on high thermal conductivity
rate of cooling is faster
efficiency calculation
useful output
————————
total input
how to increase efficiency
use insulation
made devices from materials with reduced energy transfer
use tech devices
