energy Flashcards
what is the waste energy normally
heat
what is the following for a car:
energy input
useful energy
waste energy
input= chemical
useful= kinetic
waste= heat and sound
what is the following for a lamp:
energy input
useful energy
waste energy
input- electrical
useful- light
waste- heat
what’s a sankey diagram
diagram to summarise electrical transfers taking place
can energy be created or destroyed
no it can be stored, dissipated or transferred usefully
called conversion of energy
how to work out the waste energy from a sankey diagram
useful energy- total energy
what happens to waste energy
heat energy flows away from a hotter object to its cooler surroundings
what is the efficiency
the proportion of energy supplied
transferred in useful ways
how to calculate effientcy
efficiency= useful energy out/ total energy out
what is useful energy
energy transmitted to where it is wanted, in the form it is wanted
what is wasted energy
energy that isn’t usefully transmitted
what energy spreads out into its surroundings
useful
wasted
and it becomes less useful as it spreads out, may heat up surrounding air
what is weight measured in
newtons
what is energy measured in
joules
why do machines waste energy
- friction between moving parts
- wires get hot
- air resistance
- sound created by machinery
what happens to surroundings when useful and wasteful energy is transferred
surroundings become warmer
name a problem with energy as it dissipates (spreads out)
it gets more and more difficult to use for further energy transfers
name some different forms of energy
- chemical energy (fuel)
- kinetic energy (moving)
- Gravity potential energy
- elastic potential energy
- electrical energy
can energy change from one form to another
yes eg
chemical energy in battery turns into electrical energy which turns into light energy which turns into energy heating surroundings
what happens to an objects gravitational potential energy and kinetic energy when it falls
when when an object falls and gains speed
its gravitational potential energy decreases
and it’s Kinetic energy increases
what is the conservation of energy
result meaning energy cannot be created or destroyed
conservation of energy applies to all energy changes
how can you make machines more efficient
reduce
friction
air resistance
electrical resistance
noise
can a machine be more than 100% efficient
no a machine can’t get more energy out that is put into it
what 3 ways can hear be transferred by
- radiation
- conduction
- convection
what is heat radiation
the transfer of heat energy by infrared radiation
what form of energy is coal
chemical
how is chemical energy in food transferred into someone lifting a bar
chemical in porridge > kinetic in muscles> kinetic in moving bar
