energy Flashcards
(35 cards)
whats kinetic energy?
energy of a moving object
0.5xmassxvelocitysquared
whats elastic potential energy?
amount of energy stored in a stretched spring
0.5xspring constantxextension squared
whats gravitational energy?
massxgravityxheight
how can a system be changed?
- heating
- workdone by forces
- workdone when a current flows
thermal energy
change in thermal energy=massxspecifc heat capacity x temperature change
whats the conservation of energy principle
energy can be transferred usefully, stored or dissipated but can never be created or destroyed
whats power
the rate of doing work
p=energy transfered/time or p=workdone/time
what are energy resources used for
- transport
- generating electricity
- heating
what depends on what energy resources are chosen
reliability and environmental impact
what are non renewable products
coal
oil
gas
nuclear fuel
what are renewable products
bio fuel, wind,hydroelectricity,geothermal,water waves, sun
whats efficiency
efficency=useful output energy transfer/total input energy transfer
an efficient device doesn’t waste energy, it transfers it to a useful energy store
an iffecent one dissipates most its energy
how can energy transfers be improved
by reducing the dissipation of energy’s.g lubricating a device to reduce friction or using thermal insulation
whats specific heat capacity
the amount of energy required to raise the temperature of 1kg of the substance by 1 degree
change in thermal energy/mass x temp change
dissipated energy
wasted energy
problems w required pracicle of specific heat capacity
thermal energy out in air -use insulater w blower thermal confuctivity
not all thermal energy passing into oil-ensure immersion is fully submerged
whats a series circuit
currents the same way the whole way round,byt pd difference of the cell/batery is equal to the sum of the pd of components
parallel circuits
each component independant .pd is the same across all components
whats potential difference
needed for a current to flow
current x. resistance
power=current x resistance
charge=current x time
what does the live wire do
carry current from supply to appliance
around 230v
what the earth wire do
safety wire, stopping appliance becoming live.only carries current if there’s a fault
what does the neutral wire do
complete the circuit by carrying current from the appliance back to the supply.close or at 0v
ammeter
current of circuit
voltmeter
p.d of circuit
