Topic 1 – Energy fundamentals Flashcards
what is kinetic energy
how much kinetic energy does a stationary object have?
energy stored in moving objects
none
whats the equation for kinetic energy
kinetic energy = 0.5 x mass x speed^2
what is elastic potential energy
when we stretch a spring were applying a force to change its length (doing work) we are putting in energy to stretch the spring, the stored energy is elastic potential energy
whats the equation for elastic potential energy (g)
elastic potential energy = 0.5 x spring constant x extension^2
what happens to a graph if you overstretch a spring
graph won’t be directly proportional as springs been stretched beyond limit of proportionality
extension must always be in:
metres
what is gravitational potential energy
the energy stored in an object due to its position above the earths surface
this is due to gravity acting on an object
how to calculate gravitational potential energy
gpe = mass x grav field strength x height
whats thermal energy
the energy stored due to an objects temperature
whats the law of conservation of energy
energy can be transferred usefully, stored or dissipated but it cannot be created or destroyed
whats a system
an object or group of objects
in a CLOSED system energy_____
cannot enter or leave
what are the energy transfers in a pendulum?
mass has maximum GPE, then its transferred to KE , then mass has maximum KE at bottom (mid swing) then its transferred back to GPE where it has max GPE one more
whats an issue with the pendulum example?
does not consider friction
what does friction cause (in terms of energy transfer)
causes energy to be transferred to thermal energy
energy has been dissipated as thermal energy is less useful
where is friction on the pendulum?
friction on the fixed point
friction as the pendulum pass through the air particles
what does friction cause the pendulum to do
gradually swing with less energy and eventually stop
how can we reduce unwanted energy transfers in a pendulum
remove friction by:
using a lubricant on fixed point
removing air particles from around pendulum
what are the energy changes in a bungee jumper
GPE at start,,, energy is transferred to KE as man falls.
KE store is at it max when rope JUST starts to tighten, KE store of fully extended rope is 0 (JUMPERS NOT MOVING)
all energy is transferred to elastic potential energy
ElP —> KE as rope coils
KE—-> GPE during ascent
at top, all is GPE
why will bungee jumper never return back to his original position?
energy is dissipated as thermal energy
(friction w air particles & stretching effects of bungee rope which arent fully elastic)
what is work done
when energy is transferred from one store to another
what does mechanical work involve
using a force to move an object
whats electrical work
a current transferring energy
whats the equation for work done?
work done (J) = force x distance (m)
what is power
the rate at which energy is transferred or at which work is done
what are the equations for power (W)
energy transferred (J) / time (s)
or
work done (J) / time (s)
1 watt is the same as____
1 J per second
whats the equation for effienciency
useful energy output / total energy output
or
useful power output/ total power INPUT
whys kettle more effiecnt then heating water in pan
the heating element is inside so less thermal energy lost to the environment
made of plastic which is not a good conductor so less thermal energy is lost
higher thermal conductivity means what
there will be a higher rate of energy transfer by conduction across the material
what are the two layers in modern houses
external brick and internal breezeblock
between walls is cavity
how do builders correct the high thermal conductivity of homes?
pack cavity with insulating material which has low thermal conductivity
why do houses have double glazed windows
they have a low thermal conductivity
(so less thermal energy passes through and leaves houses interior)
other than using materials w low thermal conductivity, how else can we reduce thermal energy transfer?
build house w thick walls
required practical: specific heat capacity (describe it)
place a beaker on a balance and press 0
add oil to the beaker and record the mass of the oil
place a thermometer and an immersion heater into the oil
read the starting temp.
wrap the beaker in insulating foam to reduce thermal energy transfer to the surroundings
connect the joulemeter to the immersion heater
time for thirty minutes
read total n.o of joules that passed into immersion heater
read final temp of oil
how to stop thermal energy passing out of the beaker into the air
use an insulator with a lower thermal conductivity
how to prevent not all thermal energy passing into oil (SH practical)
ensure that immersion heater is fully submerged
how to prevent incorrect reading of thermometer
use an electronic temperature probe
how to prevent thermal energy not being spread through the oil
stir the oil
how to do the thermal insulators practical (2) RP
place small beaker inside a large beaker
use kettle to boil some water
transfer 80cm^3 into a small beaker
use cardboard as a lid for large beaker (w hole for thermometer)
bulb of thermometer must be in the hot water
record start temp w a stopwatch
record temp every 3 mins for 15 minutes
repeat experiment using same vol of hot water but different insulating material
use same mass of insulating materials
whats the curve called in a temperature/time graph
cooling curves
the water will cool down _______ with the most effective insulating material
most slowly
describe practical to test wether thickness of material effects insulation
start w beaker containing 80cm^3 of hot water
(lid + thermometer)
measure temp of water every 3 minutes for fifteen minutes
repeat the experiment but wrap 2 layers of newspaper around the beaker
repeat using 4 layers and 6 layers
the more layers of newspaper, the_____ the water cools
why?
slower
more layers is a more effective thermal insulator than a few layers
what are three examples of uses of energy
transport, generating electricity , heating
what are the 3 main fossil fuels
coal, oil, gas
whats the advantages of fossil fuels
fossil fuels are reliable, always provides energy when we need it
release a great deal of energy
fossil fuels are abundant and relatively cheap
extremely versatile (v portable)
what are the disadvantages of fossil fuels
releases a huge amount of carbon dioxide
they’re non-renewable as they’re not being replenished
can release other pollutants
whats the disadvantages of nuclear power
nuclear power is non-renewable, they run on uranium and plutonium
contains highly dangerous radioactive materials. if there’s an accident they could be released to the environment.
decommissioning a power plant takes many years and is extremely expensive
nuclear power plants generate a large amount of highly dangerous radioactive waste. this must be stored for thousands of years before its safe
whats the advantages of nuclear power
once running it releases NO carbon dioxide so doesn’t contribute to climate change
its v reliable. It generates lots of electricity exactly when we want it
The uk has _______ of coal. Up until 1950s almost ____________ generated by Uk came from _______
abundant reserved of coal
all of the electricity
burning coal
coal and coal gas were also used for almost all ____ and cooking in the UK
heating
in the 1950s, nuclear power came online and by the 1980s this produces around ____ of the uks electricty
20%
in the 1970’s the Uk became a big producer of what?
this began to replace ____
oil and gas
coal for electricity generation
what are the advantages of burning gas over coal?
generates less carbon dioxide than burning coal, this contributes less to climate change
gas-fired power stations are flexible, they have a short start up time whereas coal fired power stations have a long start up time
what does a short start up time mean
they can be switched on quickly during periods of high demand
what was an economic factor of using fossil fuels
v cheap, switching from them could cost money and cost jobs
in 2005, the Kyoto Protocol committed countries to____
reducing greenhouse gas emissions
why is nuclear power ideal
we need a baseload (a constant supply of electricity that’s on all the time)
what can we use gas-fired power stations to provide what
emergency power in times of peak demand
what types of gas provide what in Uk energy
renewables provide the bulk of our electricity , nuclear provides a baseload and gas provides electricity during periods of peak demand
what is a renewable energy resource
a resource that is being or can be replenished as its used
name the types of renewable energy
wind, solar, hydroelectric, tidal, biofules, geothermal, wave.
what are the advantages of renewable energy
will never run out
do not add CO2 to the atmosphere so don’t contribute to climate change
whats the disadvantage of wind and solar power
not reliable, some days are not windy/ sunny
whats the advantage of hydroelectric
whats the disadvantage
v reliable
habitats are destroyed when dams are built and valleys are flooded
also only useful in countries w lots of rivers so not suitable for uk
whats the advantage of tidal power
whats the disadvantage
its extremely reliable
(atm the uk doesn’t generate any electricity from it)
may be harmful to wildlife
whats the advantage of wave power
whats the disadvantage
wave power is reliable and has huge potential in the UK which has an extensive coastline
its v small scale and experimental atm
what is geothermal energy
geothermal energy uses heat from the earth to generate electricity and heat buildings
whats the advantage of geothermal
whats the disadvantage
v reliable
not used much in the UK
what are biofuels produced from
plant materials
whats the advantages of biofuels
whats the disadvantage
don’t add EXTRA carbon dioxide to the atmosphere so are carbon neutral
&
potentially v useful as we can use them to power vehicles such as cars and buses.
if we use land to grow crops for fuel, that could push up the price of food
