P7 Flashcards
what is work
the amount of energy transferred
what is the equation for work
work = force * distance
what is the unit for work
joules
what is the unit for force
newtons
what is the unit for distance
metres
what is power
the rate at which energy is transferred/supplied
what is the equation for power
power = energy/time
what is the unit for power
watts
what is the unit for energy
joules
what is the acronym for energy stores
green sick
what are the energy stores
- gravitational potential
- radiant (light)
- electrical
- elastic potential (strain)
- nuclear
- sound
- internal (thermal)
- chemical
- kinetic
how is energy transferred between stores
- forces (mechanical work done)
- electrical currents (electrical work done)
- heating
- electromagnetic/sound/other waves
what is the principle of conservation of energy
energy can neither be created nor destroyed, only be converted from one form to another
what is the equation for kinetic energy
KE = 1/2* mv^2
what is the equation for gravitational potential energy
gpe= mgh
how is efficiency calculated form energy and power
(useful energy output/energy input) *100%
(useful power output/power input) *100%
what is the spring constant
force per unit extension
what is hooke’s law
extension of elastic object is directly proportional to load force being applied
what is equation for spring constant
k = F/x
what is the limit of proportionality
the “limit” force that can be applied before F & x stop being directly proportional
how to work out spring constant on graph
gradient
examples of renewable energy sources
- wind
- geothermal
- water (wave, hydroelectric, tidal)
- biomass/biofuel
- heat/light from sun
examples of non-renewable energy sources
- fossil fuels
- nuclear fission
how is energy obtained from chemical energy stored in fuel
- set on fire
- which boils water to spin turbine
- or used in combustion engine
how is energy obtained from waves
- buoy bobs up and down on waves
- turns turbines
how is energy obtained from tides
- flow of water turns generator
how is energy obtained from hydroelectric dams
- water flows downhill (gpe–>ke)
- spins turbine
how is energy obtained from geothermal resources
- heat from earth evaporates water
- spins turbine
how is energy obtained from nuclear fission
- nuclear fuel rods get hot
- heat gas (often water) to spin turbine
how is energy obtained from heat and light from sun
- cells: sunlight creates voltage across semiconductor material
- panels: sunshine heats water in tank
how is energy obtained from wind
- as wind passes, spins turbine
what are the steps in a power generator
- boiler: chemical to internal
- turbine: internal to kinetic
- generator: kinetic to electrical
- transformer: change voltage
what are advantages of fossil fuels
- easy to use (burn it)
- can be transported to where needed
- cheap
disadvantages of fossil fuels
- burning releases greenhouse gases: global warming
- harm environment (oil spills, soot from coal)
advantages of wave energy
- plentiful space out at sea
- renewable
- plentiful in windy places
disadvantages of wave energy
- seawater corrodes machinery, maintenance challenging
- far away from cities/industries
advantages of tidal energy
- reliable: happens every day as earth turns
- renewable
- no harmful gases produced
disadvantages of tidal energy
- require suitable location
- expensive to build
advantages of hydroelectric dams
- renewable
- very short start-up/response time
disadvantages of hydroelectric dams
- location dependent (hilly, wet places, not flat)
- can be expensive to initially construct)
advantages of geothermal energy
free and renewable
- no greenhouse gases
disadvantages of geothermal energy
- dependent on location
- hot areas more accessible in tectonically active places
- initial cost to build infrastructure
advantages of nuclear fission
- high energy density
- no greenhouse gases produce
disadvantages of nuclear fission
- radioactive waste
- expensive to build
advantages of heat and light energy from sun
- sunlight free and reliable in some places
- easy to install
disadvantages of heat and light energy from sun
- require large surface area to provide reasonable amount of power
advantages of wind energy
- renewable
- works well anywhere with wind
disadvantages of wind energy
- dependent on wind
- moderately expensive to build
what is the source of tidal energy
moon
which energy resources have the sun as the source
all except tidal, geothermal, nuclear
how is energy released in the sun
nuclear fusion
