energy Flashcards
what is the rule for energy
it is never created or destroyed but only transferred between different objects and forms
list some energy stores
thermal -heat
kinetic-movement
gravitational potential-position in gravitational field
elastic potential- held in already stretched spring
chemical-held by chemical bonds
magnetic
electrostatic
nuclear-breaking atoms apart
what are the 4 ways we can transfer energy
mechanically-physically stretching an elastic band
heating-
through radiation -like light or sound waves
electrically-plugging item into socket
what happens when a system changes and how does it happen
energy is transferred between different objects or different forms
what is a system
collection of matter
what can happen in an open system that cant in a closed-give an example
no matter or energy can leave so overall change is 0
kettle is connected into plug socket
electrical energy flows to heating element(Transferred electrically) of store warming metal heating element transferring it to the waters thermal energy store
what is work done = to and what are the 2 types
it equals energy transferred
mechanical(using force to move object)-chemical energy from your leg when kicking a ball transferred to kinetic energy store of ball
and electrical(when current flows) energy required to overcome resistance in the wires of a circuit
what is the equation for kinetic energy
e =1/2 mv2
what is the equation for gravitaional potential energy
e=mgh
what is the equation for elastic potential energy
e=1/2ke2(extension-m)
(spring constant-N/m)
what is the equation for thermal energy
E=mc x change in temp
efficiency equation
useful nrg out/total nrg in x100
or power
what are some finite energy sources
coal oil/natural gas
what are renewable
wind/hydoelectric/solar/geothermal/biofuel
what is internal enrgy
sum of potential/kinetic energy
what is specific latent heat
energy required to change state of substance
what is the relation of mass and speed and kinetic energy
the faster an object moves the more kinetic energy it has
the more mass an object has the more kinetic energy it has if everything else is constant
how many kilos in a tonne
1000
what is gravity
the force of attraction between 2 objects which is dependent on mass and the distance between the objects
what is the gravitational field strength on the earth and mars
9.8N/kg and 1.6N/kg
what is weight
the force of attraction an object experiences when entering a gravitational field
weight/ mass and gravitational field strength
w=m(kg)g(9.8)
what is the formula for gravitational potential energy
ep=mgh
kg/n/kg/m
what is gpe
the energy transferred to the objects potential energy store to lift up an object
as an object rises what happens
ke is converted to gpe
gpe or ke lost=
ke gained or gpe gained
what is internal energy
potential energy stores and kinetic energy stores
-total energy stored by particles of a substance
what is the equation for specific heat capacity
change in internal energy=mass x spec heat capacity x change in temp
what is the specific heat capacity
amount of energy needed to raise the temp of 1 kg of a substance by 1 degrees
what is temperature
average internal energy of a substance
v
what is conservation of energy
energy can be transferred stored or disspated but cant be created or destroyed
what forms can wasted energy come as
heat mainly
what are the 3 ways heat is transferred
conduction in solids
convection in liquids
radiation through empty space
why does conduction mainly happen in solids
as they collide a lot unlike in liquids or gases where they are spread out
what do you use to measure how well objects transfer energy by conduction
thermal conductivity
what is convection current
hotter particles spread out and are replaced by colder particles which go near heat source and then these cool down and repeat
what are some example of convection current
radiation and oceans
what does a fluid refer to
a substance that has particles that are free to move like liquids or gases
how do we reduce thermal energy that escapes our house
ensure door is sealed closed(convection so air cant escape)
thick cavity walls(with low thermal conductivity)
conduction vs insulation
conduction is how heat moves through a material
insulation is keeping heat and not allowing it to flow
double glazed windows
how do we reduce friction
using lubricants
making cars and planes streamlined
what is the 1st equation for power
power is the rate at which energy transferred
p=e/t
2nd equation for power
p(watts)=w(joules)/t(s)
power is the rate that work is done
why is no device 100% apart from some
they all produce some form of waste mainly thermal energy
apart from heaters which all energy would go into heat
what are some non renewable energy sources
coal
oil
natural gas
nuclear energy
what are some renewable resources
solar
wind
hydroelectric
geothermal
tidal
biofuels
what non renewable energy mainly used for
natural gas for cooking
coal for fireplaces
crude oil for petrol and diesel(transport)
what is a renewable form of heating
biofuels can be burned for heat just like coal
solar water heaters use suns energy to heat water and pump through our heaters
Explain the difference between renewable and non-renewable energy resources. Use an example for each.
A renewable energy resource is one that is being replenished as quickly as it is used. For example solar energy is renewable because new sunlight is always being generated by the sun - we don’t use it up.
A non-renewable energy resource on the other hand is one that isn’t being replenished and so has a limited supply. For example fossil fuels like coal are non-renewable because they’re not being replenished and at some point coal could run out.
what are some ways fossil fuels can be used
to generate electricity
burned to provide heat
to generate electricity
what are the pros and cons of fossil fuels
pros
-relatively cheap
-can be used in any condition(dont require certain like sunlight)
-many of our modern infrastructure are designed to run on it
cons
-limited
-produce co2 when burned so contribute to global warming
-produce toxic gases when burned
pros and cons of nuclear energy
Pros
-dont produce any pollutants
-used in any conditions
-unlikely to run out in a long time
Cons
-finite
-produce years of radioactive waste which remain harmful for 1000s of years
-expensive
-small chance of nuclear meltdown/accident
what is wind power/how is it generated and used
caused by wind turbines with a generator turns generator when wind flows which converts kinetic energy from movement electrical energy which is sent to national grid
what is solar power
solar cells generate electric current from sunlight
-in watches or calculators
can be used to generate eletricity for towns
what are pros for solar and wind energy
pros-
-low running costs
-no pollutants produced
-dont damage environment
-get cheaper every year
cons-
-weather dependent
-no way to increase supply in peak demand
-take up lots of space
-high up front costs
-production produces pollutants
what is geothermal energy/uses
thermal energy generated and stored in earths crust
used for heat and electricity
what are cons/pros of geothermal energy
cons
-can only be used in certain areas
-power plants can be expensive to build
pros
-only damages environment slightly
-doesnt produce any pollutants while running
-reliable over long periods
what are biofuels
fuels made from recently living organisms(plants or algae) as they photosynthesis and lock up suns energy which we release later when we burn for fuel
why are biofuels carbon neutral
they took up co2 when they were growing and when they are burnt they release it so there is no overall release of co2
what are pros and cons of biofuels
pros
-cheap to make
-easy to transport
-can be mixed with fossil fuels and used in vehicles we already have
-good substitute for fossil fuels
cons-
-processes release co2 and require lots of energy
-damage environments as we need large space to grow
In theory biofuels should be carbon neutral, but in reality they are not.
Trees may be cut down, so no longer absorb CO2
Trees may be cut down, and will release CO2 if burned
Energy will be required to harvest, process and transport the biofuels…
… which will release more CO2
what are the pros and cons of tidal and hydroelectricity
pros
-reliable
-low running costs
-large amounts of energy with 0 pollution
cons-
-often flood huge areas
-initial set up is expensive
-sometimes stop boat and fish travelling
what are the variables for the spec heat capacity practical
independent-material type
dependent-temp rise
control-mass of material/surface of material
list the spec heat practical equipment
heater
block of material
power supply/pack (10v)
Ammeter
wires
leads
thermometer
insulating material
stopwatch
what are the steps for the practical of shc 8 steps
1)get block of material with a hole for the heater and the thermometer
2)Measure mass of block and wrap in insulating material(like foam or thick newspaper)
add heater and thermometer
3)measure the starting temp of the block and set the pd of the power supply as 10v
4)Turn the power supply on and start a stopwatch
5)Measure the temperature at eye level every minute for 10 mins
6)look at the ammeter to check if the current changes as it should stay constant
7)when all readings are collected turn off power supply
8)with data find materials spec heat capacity and repeat with differet materials
how do you calculate spec heat capacity from your data
use p=vi to find out how much power has been supplied to the heater
then use e=pt to find energy transferred to the heater
plot graph of energy transferred(x axis) against temperature(y axis)
find gradient of straight part of the graph
spec heat capacity= 1/ (change in gradient x mass of the block)
what is the equipment in the insulation practical (6 steps)
boil water in a kettle and pour into a beaker (sealable container) to a safe level
use thermometer to get starting temp of water
seal beaker and leave it for 5 mins measuring using stopwatch
remove lid and measure the final temp of the water
pour water away and let container cool at room temp
repeat experiment but wrap container in different material using same mass of water and reboiling water
Why is it important to repeat the experiment?
To ensure accuracy and consistency of results
